Renewable energy scenarios for South Karelia – non-industrial energy demands

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Degree Program in Energy Technology

Jori Lindgren

RENEWABLE ENERGY SCENARIOS FOR SOUTH KARELIA – NON- INDUSTRIAL ENERGY DEMANDS

Examiners: Professor Esa Vakkilainen Professor Jero Ahola

Supervisors: Lic.Sc. (Tech.) Simo Hammo MSc Michael Child

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TIIVISTELMÄ

Lappeenrannan teknillinen yliopisto LUT School of Energy Systems Energiatekniikan koulutusohjelma

Jori Lindgren

Uusiutuvan energian skenaariot Etelä-Karjalalle – julkisen sektorin, liikenteen sekä rakennusten energiatarpeet

Diplomityö

2016

113 sivua, 42 kuvaa, 8 taulukkoa, 10 liitettä

Työn tarkastajat: Professori Esa Vakkilainen Professori Jero Ahola

Hakusanat: uusiutuva energia, energiajärjestelmä, mallinnus, Etelä-Karjala, energiasuunnittelu

Tässä diplomityössä tarkastellaan täysin uusiutuvaa energiajärjestelmää Etelä-Karjalan maakunnan alueella, mikä onkin jo tällä hetkellä Suomen uusiutuvin maakunta.

Diplomityössä tarkastellaan julkisen sektorin, liikenteen ja rakennusten energian kulutusta mutta teollisuuden energiankäyttö jätetään tarkastelun ulkopuolelle. Työssä tutustutaan tämän hetken Etelä-Karjalan energiajärjestelmään ja sen perusteella tehdään referenssi- skenaario. Tulevaisuuden skenaariot tehdään vuosille 2030 ja 2050. Tulevaisuuden skenaarioissa muutos keskittyy järjestelmän sähköistymiseen ja uusiutuvien tuotantomuotojen integroimiseen järjestelmään. Sähköistyminen kasvattaa sähkönkulutusta, joka pyritään kattamaan uusiutuvilla tuotantomuodoilla, lähinnä tuuli- ja aurinkovoimalla.

Liikennesektori rajataan kumipyöräliikenteeseen ja sen muutos tulee olemaan haastavin ja aikaa vievin. Muutokseen pyritään liikennepolttoaineiden tuotannolla maakunnassa sekä sähköautoilulla. Uusiutuva energiajärjestelmä tarvitsee tuotannon ja kysynnän joustoa sekä älyä järjestelmältä. Työssä tarkastellaan myös järjestelmän kustannuksia sekä työllisyysvaikutuksia.

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ABSTRACT

Lappeenranta University of Technology LUT School of Energy Systems

Degree Program in Energy Technology

Jori Lindgren

Renewable energy scenarios for south karelia – Non-industrial energy demands

Master’s Thesis

113 pages, 42 figures, 8 tables, 10 appendix

Examiners: Professori Esa Vakkilainen Professori Jero Ahola

Keywords: renewable energy, energy system modelling, South Karelia, energy planning

The thesis introduces a fully renewable future energy system for a region of South Karelia, which already has the biggest renewable energy share in Finland. The thesis analyses the public sector, transportation and building’s energy demand, leaving industry out from the analysis. A brief introduction to the current state of the energy system is made and reference model is built around this. A future scenarios are built for years 2030 and 2050. The focus in future energy scenarios is electrification of the system, which is considered to be a way to integrate the new renewable production in the whole system. The electrification pathway increases the electricity consumption in the region which is met with increased renewable energy production, mainly wind and solar power. The transportation sector is limited to road traffic only. The transportation sector is the most challenging and likely to be the most slowly changing sector. Traffic fuel production is implemented in the region and electric vehicle usage is increased. The renewable energy system requires production and demand side flexibility and intelligence. The costs and employment effect is also considered and calculated.

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ACKNOWLEDGEMENTS

This thesis has been conducted as a part of the Academy of Finland and Strategic Research Council’s Smart Energy Transition – project. Lappeenranta city has been the principal of the work and I’d like to thank especially Markku for the feedback and positive attitude towards the work. I hope the best of luck to Lappeenranta conquering the challenges and being the showroom and example of future green city of Finland.

I’d like to thank my supervisors Jero and Simo for the feedback and ideas on my work and especially Michael who’s been the technical support and assist with the EnergyPLAN program. Thanks to Professor Esa Vakkilainen as well for the feedback and comments on my thesis. I can’t thank enough all my friends during my time in Lappeenranta for helping to conquer the studies and easing the mental burden. The dearest thanks to my family for supporting me in the choices I’ve made in my life and in my studies leading to this very thesis.

12.7.2016 Lappeenranta

Jori Lindgren

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SYMBOLI- JA LYHENNELUETTELO

CAES Compressed Air Energy Storage CCR Carbon Capture and Recycle

CEEP Critical Excess Electricity Production CHP Combined Heat and Power

CO Carbon monoxide

CO2 Carbon dioxide

COP Coefficient of Performance DH District Heating

EEEP Exportable Excess Electricity Production EV Electric Vehicle

G2V Grid to Vehicle

H2 Hydrogen

HP Heat Pumps

P2G Power to Gas

P2V Power to Vehicle PES Primary Energy Supply

PHES Pumped Hydro Electric Storage

PP Power Plant

V2G Vehicle to Grid

GWh Gigawatt hour

Mt Megaton

MWh Megawatt hour

t ton

TWh Terawatt hour

W Watt

Wh Watt hour

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1 INTRODUCTION

1.1 Background

The transition to renewable energy is on-going at this very moment. Countries may have different drivers but generally speaking, securing the energy supply and reducing dependency on imported energy seems to be one of the main motivations [1]. One of the reasons behind Energiewende in Germany, is the increased opposition towards nuclear power which led to the government’s decision to decommission nuclear power plants by the end of the 2022 [2]. In China, securing energy supply and the worry of the air quality is driving renewables to the energy mix [1, p. 10]. Denmark is breaking records in renewable energy shares [3] [4] and made a record of a single wind turbine producing enough to power 13 500 households in 24-hour period [5]. The energy transition is happening so fast even the freshly made scenarios are including old information [6]. Whether Finland wants to be part of this transition and its opportunities, should be decided very soon. The transition is justified not only by the environmental effect but the socio-economic aspects too such as employment, increased gross domestic product, education, health and reduced poverty [7].

Another reason for the energy transition is the worry of the environmental impact of fossil fuels to the global warming. There are studies for and against it. However, it has been statistically justified that the CO2 in the atmosphere has risen due the industrialization and burning of fossil fuels [8]. Decreasing and stopping CO2 emissions has been the target of many global agreements, the most recent one being the Paris agreement in the end of 2015, which was signed by 175 nations [9]. In 2009 the European commission published an agreement which goal is to reduce the greenhouse gases, increase the share of renewable energy sources (RES), and increase the energy efficiency and the share of biofuels in the transportation sector. This is so called RES-directive (2009/28/EC) [10]. There are goals for each country in EU in the directive. The goals for Finland for example are 38 % share of RES in total energy consumption and 20 % share of RES in the transportation sector.

There are several projects and networks in Finland concerning the energy transition. Smart Energy Transition (SET) is a project to identify Finland’s opportunities in the ongoing energy distortion [11]. Finnish Sustainable Communities (FISU) is a network of cities which are aiming towards carbon neutrality by 2050 [12], similar to HINKU network [13]. Neo

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Carbon Energy – project focus on smart energy system solutions such as storages and digitalization [14]. Even though the numerous projects are trying to find answers for the Finnish energy sector, the new renewable energy sources are yet to become any major role in the Finnish energy palette. The energy supply should be diverse and even though the biomass usage in Finland speaks for itself, there are differing opinions what will be the sustainable level of biomass usage.

The key to increase the share of renewables is to tackle the challenges they bring with the heavy fluctuating production. Wind and the solar energy output varies yearly, monthly and even hourly while the production and demand must be equal any given time. New types of energy storages and production and demand side flexibility are some of the suggested solutions for this. It is important to integrate the new renewables to the whole energy system, including heat and transportation sector.

1.2 Goals and delimitations

The goal of the thesis is to model future energy systems for South Karelia but also to identify the current status of it. The modelling is carried out with a tool called EnergyPLAN provided by a university of Aalborg from Denmark. Three different years are modelled, a reference year of 2012, mid-goal scenario for 2030 and fully renewable scenario for 2050. Another goal of the thesis is to present a detailed solution for fully renewable energy system based on the chosen pathway. The thesis emphasises on self-sufficiency and electrification of the selected sectors. Electrification is a way to integrate the new renewable resources to the whole energy system. Other pathways are possible but not discussed in the thesis. An hourly based simulations are made with the modelling tool and the simulations are used for deeper analysis of the system behaviour. The results focuses on the primary energy supply, electricity production and consumption, emissions and costs of the energy system. An employment effect is also estimated.

The industrial energy usage and production is limited out from the thesis, meaning the thesis only covers the public sector, transportation and building’s energy demand. Limiting the industry will cause a slight problem with the production mix. For example, hydro power in the region would be enough to cover the demands of the three sectors (electricity wise). The

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industrial need has to be identified and the rest of the production mix then reduced by the amount. The transportation sector is chosen to cover only road traffic (trucks, buses, passenger cars, vans etc.).

There are a lot of technologies which could provide answers to the fully renewable systems and they are not all considered or discussed in the thesis. For example, solar heating systems are not taken into consideration, geothermal is also left out. Electricity storage is only discussed with vehicle-to-grid technology as Finland is seen to have minimal potential with pumped hydro storage which is the prevailing storage method at the moment. Also transportation fuels produced in the future scenario and the pathway chosen may not be the most efficient or the cheapest. There is no clear winner-technology at the moment which could be seen as the only way. Different solutions should be then discussed.

1.3 Structure of the thesis

The chapter 2 introduces which drivers are currently affecting the transition in the energy systems. Chapter 3 introduces some of the technologies which could provide solutions to the fully renewable systems. Main focus in the chapter is to introduce the technologies used in the modelling, limiting some potential technologies out from thesis. The current status of the South Karelia’s energy system is discussed in the chapter 4. Chapter 5 introduces the tool used for modelling the energy systems and chapter 6 introduces the method, data and differences of the scenarios built for South Karelia. Chapter 7 focuses on the results where as chapter 8 provides discussions related to the results, for example challenges and benefits.

Chapter 9 is a short summary of the thesis’ main results.

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2 DRIVERS FOR RENEWABLE ENERGY TRANSITION

The growing energy consumption and the climate change are driving the energy transition on a global scale. This chapter explains in further detail the political, environmental and economical drivers for renewable energy transition. Some of the mutual policies in Europe are introduced but the focus is mainly on the Finnish national level. The international strategies and policies are based on the United Nations (UN) climate and energy agreement, so called Kyoto agreement. The policies are mainly the legislative drivers whereas social, environmental and economical are more of a choose awareness drivers. Sustainability and green ideologies are gaining popularity worldwide. Sustainability allows the use of resources, support economic production and containing well-being indefinitely [15].

One could also add social drivers for the renewable energy transitions. Social drivers could be related to such as lifestyle, ethics, equality, quality of life, education and development of communities. As the information and education of the renewable energies grow, one may demand for better, sustainable solutions. The renewable energy resources are more widely available on the planet reducing the energy poverty in the world and increasing the equality regarding energy supply. Everyone on the planet are entitled to the modern energy services, which is crucial to the economic development as well. According to a report by International Energy Agency (IEA), approximately 1,2 billion people are without access to electricity [16].

2.1 Policies

Directives are a guides for legislation. The directives do not directly interpret the law and they only work as a guideline. There are several directives in use in Finland. These are such as; eco-planning, energy service, energy labelling, emission trading, building’s energy efficiency and renewable energy directive. Energy service directive focuses on the energy end use. It is essentially a guideline for energy efficiency methods in the national level. This directive makes sure the public sector has the necessary means to carry out the energy efficiency actions. The energy labelling is a way of comparing the energy efficiencies of different machines used in households and offices. These labels are mutual in the EU countries. The emission trading is a mean to reduce the CO2 emissions in the EU countries.

The emission trading directive gives guidelines for example how the emissions are verified

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or calculated, and also how to require the emissions permissions. In Finland the permissions are handled by Energy Authority (Energiavirasto). The guidelines for energy efficient building is set in the Building’s Energy Efficiency-directive. The directive consists mainly of three major topics; energy certificates, minimum requirements for energy efficiency and boilers’ and air conditioners’ scheduled maintenances. These are the basics for building’s energy efficiency is improvements. Finally, the renewable energy directive gives goals for each EU member country to increase their renewable energy production. For Finland the goal is 38 % renewable energy share (RES) by the year 2020. The goal was already met in 2015. [17]

Besides the EU and UN based strategies, Finland has its own national energy strategy. The international strategies give guidelines but Finland has increased some of the goals in a national level. For example, transportation sector has a goal of 10 % RES in EU level however Finland increased the share to 20 % on a national level. Another long term goal for Finland is to reduce the emissions by 80 % by 2050. The national strategy also calls for measures to be taken in a province, city or a county level. Most of the provinces in Finland have adopted this, and have made their own energy strategies. All the small scale strategies contribute and aid to achieve the national goals. [17].

Subsidies, feed in tariff, taxation are examples of promoting renewable energy production financially on a national level. Subsidies are financial support from the government to promote the renewable energy investments or energy conserving methods. The subsidy could also be received for energy surveys in Finland. Feed in tariff is a payment which ensures a fixed price for an electricity producer. This is often received for a wind power production but it can be received for biogas plant or a wood based fuel plant. In Finland the feed in tariff is fixed price of 83.5 €/MWh. The government pays the difference of the feed in tariff and the market price. Taxation is another way of promoting renewable energies.

Whether it is tax relief or an increase in taxation is up to the pros and cons weighted in the decision making. [17].

Green certificates or renewable energy certificates (REC) are a way of guaranteeing or proving a renewable electricity production for the end-user. It is impossible to separate

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renewable electricity from fossil fuel electricity in the electricity grid. With the certificate, one can guarantee that a share of the electricity production comes from renewable energy sources. The REC’s are created through the electricity production; one MWh of electricity creates one green certificate. [17]

2.2 Environmental

Mitigating the global warming is seen as the main driver in the energy transition and behind all the climate and energy strategies in the world. The global warming is explained with the increased CO2 content in the atmosphere as it contributes to the greenhouse effect. The CO2

emissions in atmosphere and the planet’s temperature seem to follow a similar pattern [8].

The CO2 content in the atmosphere varies naturally but there has been a considerable increase in the content since the industrialisation. The goal of the new agreement in Paris in 2015 was to implement actions to limit the global warming by 1.5 degrees. However, the actions to reduce the CO2 emissions in the agreement are not sufficient to meet this demand.

Another motivation for the energy transition is the fact that the natural fossil fuel resources and reserves are depleting. There are numerous reviews and estimates of the world fossil fuel reserves and their depletion rate. They seem to agree that oil and natural gas will run out in 50+ years and coal reserves will last the longest, approx. 100 years with the current consumptions and reserves. New reserves might be discovered though but may not be easily accessible. [18].

The life cycle emissions of renewable energy are not however CO2 free, yet. The manufacturing of components, logistics and extraction of the raw materials can rarely be implemented with fully renewable system. However, as the renewables penetrates into the energy system, the less CO2 emissions will be released in manufacturing or transportation.

More critical question will be the availability of the rare minerals needed for the new renewable technologies.

2.3 Economical

Like with any other business sectors, money is the most important factor for stakeholders. It is the fact that no business will grow without profit, whether it comes with the help of

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subsidies or with the least cost choices and sales margin. The renewable energy technologies are usually associated with high costs. However, the renewable energy technology costs have been reducing in a fast pace in recent years. International Renewable Energy Agency’s (IRENA) statistics show how the renewable’s levelised cost of energy (LCOE) has come down to compete with the traditional fossil fuel based technologies [19]. The price development is presented in the Figure 1. LCOE is a measure to compare different technologies’ lifetime costs over a lifetime energy output.

Figure 1. LCOE of utility-scale renewable energy technologies in 2010 and 2014 [19, p. 1].

In addition to the technological price, IRENA conducted a report about the socio-economic effects of wind and solar power. The socio-economic benefits are such as the increased gross domestic product (GDP), employment effect, added value and improved trade balance.

According to the report the global GDP will increase between 0,6 % and 1,1 % if the renewable share is doubled. The global trade will change as the fossil fuels are replaced. The trade balance with countries importing fossil fuels will most likely improve. [20].

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According to IRENA, in 2014, the amount of jobs in renewable energy sector was estimated to 7,7 million worldwide excluding large hydropower. This is 18 % increase compared to the previous year. The largest employer being PV (photovoltaics) with 2,5 million jobs, the second largest being biofuels with 1,8 million jobs. Wind power employs 1 million people world-wide. Most of the jobs are in manufacturing and geographically they’re mostly in China, Brazil and United States and of course spread throughout the Europe. [21]. Even though the renewables will reduce the jobs in the fossil fuel business, the net effect on the employment will be positive [20, p. 44]. The renewable energy production development consists measures such as of project planning, manufacturing, installation, grid connection, operation and maintenance and decommissioning [7]. All these actions will require employers, whether it is manufacturing certain components such as inverters, gearing, solar cells, rotor blades etc., feasibility studies, legal activities, design planning, grid operating, electrical or any other work requiring workforce. The domestic value could be significant in the employment if carried out domestically [7].

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3 TECHNOLOGIES IN RENEWABLE ENERGY SYSTEMS

This chapter introduces the reader to the renewable energy production and storing of energy.

The basic principles of the energy conversion methods are introduced. It is not considered necessary to go deep into the details but only to introduce the reader to the schemes and technologies used later in the energy system modelling. Some potential future technologies are not introduced here such as the smart grids, solar or geothermal technologies which can be potentially used in the future energy systems. The global capacities are introduced with respective technologies and Finland’s potentials are also mentioned.

3.1 Wind power

The world-wide utilisation of wind power has increased substantially in the 21^st century. The wind energy potential in the world is estimated to be around 1 million GW. The wind power capacity in the world has been doubled every three and half year since 1990. In 2015 the total installed capacity in the world was over 430 GW. The total capacity increased over 60 GW in 2015, breaking the all-time growth record. The largest growth happened in China with total of 30 GW new installed capacity. China is also the world leader in installed capacity with total of 145 GW. United States comes 2^nd with total capacity of 74 GW and Germany being 3^rd with 45 GW. The growth in US and Germany were 8,6 GW and 6 GW respectively. [22]. The installed wind power capacity in Finland has grown in a steady pace in the recent years. The installed capacity in 2015 was 1 GW with an increase of nearly 400 MW from the year 2014. The power production covers nearly 3 % of the Finnish electricity consumption. The wind power projects in Finland in 2013 covered approximately 11 GW of installed capacity. [23].

The advantages wind energy have is its well-known technology, vast resource, emission-free production, lack of fuel costs and fast installation. As with other renewable energy sources, wind power has to face some major barriers. There are several barriers that are mentioned in [24] which are related to environment, social acceptance, technical and financial aspects.

One main social acceptance barrier is the proximity of wind turbines to buildings. It is said to have negative impact to landscape, noise and shadow flicker. The environmental barrier is also high with the effect to the natural habitants near the wind turbines. There is also a concern how the turbines affect to the communication systems (military, meteorological,

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aviation, telecom radars). The financial barriers are related to the high investment costs, uncertainty (electricity price, policies, and investors), possible increase in operational cost of the power supply system and cut down of subsidies which affect the competitiveness compared to other production units. There are some technical barriers such as the intermittency and grid stabilisation which might lead to negative impact on electricity quality and these may lead to the need for changes in the power market in general.

There are few kinds of policies in order to help the market penetration for wind energy. Feed- in tariff is a system where wind energy producer is guaranteed a certain price from the electricity produced. The subsidy is then the difference of the electricity market price and the fixed (guaranteed) price. Renewable Energy Certificates (REC) is a concept similar to emission trading. It is part of quota where electricity producers are given terms of a certain share of renewable in the total production mix. If these terms aren’t met, penalties are implemented. One REC is created from one MWh of electricity. These are then traded to meet the terms between the producers. Taxes or generation based incentives are another supportive system to wind and other renewable resources. [25]. These incentives are usually ways of decreasing certain costs for producers.

Wind energy utilisation is not a “new” or “revolutionary” when it comes to the technology and principle. The principle of wind energy is capturing the kinetic energy of air mass. The kinetic energy through the wind turbine can be calculated as follows [26, p. 11]

𝐸_𝑘 =¹

2𝜌𝐴𝑣_𝑤³ =¹

8𝑑²𝜌𝑣_𝑤³ (1)

where Ek = kinetic energy ρ = air density

A = swept area of the turbine blades v = wind speed

d = diameter of rotor blade

As seen in the equation the kinetic energy depends on the second power of the diameter of the rotor blades and the third power of the wind velocity. It equals that when wind speed is

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doubled, the power extracted is increased by factor eight [27, p. 236]. This means the wind speed is in a major role in designing and planning of wind turbines. As the wind’s kinetic energy converts into the rotational movement of the rotor blades, the wind must slow down.

This consequently means there have to be a ratio of wind speeds, before and after the wind turbine, that produces the maximum power. The ratio is called coefficient of power cP. It was first introduced by Albert Betz in 1920s and it could be interpreted as the efficiency between rotor blade and the wind. Figure 2 shows the relativity of the wind speed ratio and the cP. The theoretical maximum power coefficient is 16/27 or 0,593. This is known as the Betz’s law. Ideally a wind turbine slows the wind speed down to 1/3 of its original speed.

[25, p. 22].

Figure 2. The relativity between the wind speed ratio and the power coefficient [28, p. 300].

An important design value of wind turbines is the tip-speed ratio λ. It is the ratio of circumferential velocity of the blade tips and the wind speed. The ratio influences the efficiency of the wind turbine. Basically if the λ is too small, the flow breaks and reduces lift force. If the λ is too big, the lift force is at its maximum but reduces power efficiency.

[25, pp. 12-13]. The correlation between power coefficient and the tip-speed ratio can be seen in the Figure 3. The tip-speed ratio can be calculated as follows [26, p. 12];

𝜆 =^𝑢

𝑣 = ^𝜔𝑟

𝑣 = ^𝑑𝜔

2𝑣 =^𝑑𝜋𝑛

𝑣 (2)

where λ = tip-speed ratio

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u = circumferential velocity ω = angular speed

r = radius of the turbine swept area d = diameter of the turbine swept area n = rotation speed

Figure 3. Power coefficient over tip-seed ratio of different rotor types [26, p. 13].

Wind speed is the most important factor in the decision making of wind turbine installations.

Wind measurements are used for identifying the most potential lands and areas for wind power utilization. LIDAR (LIght Detection And Ranging) technology is one of the many possible ways of measuring the wind conditions. Once wind conditions are measured in a certain area, a tool is used for modelling the conditions in wider area. WAsP program is a standard tool in the business for modelling the wind conditions. The program takes the surface roughness, landform and building’s effect on the wind conditions into consideration [29]. A tool called Finnish Wind Atlas is used in Finland which is based on weather prediction model AROME and WAsP model. Wind Atlas includes wind conditions for different altitudes, mean wind speeds, wind directions and estimations for wind energy production. [30].

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3.2 Solar power

Solar energy can be tapped with either thermal conversion or direct conversion to electricity.

This thesis focuses on the latter, direct conversion to electricity through photovoltaics (PV).

The renewable markets are growing rapidly and PV markets makes no exception. In 2015, the installed capacity of PV grew 50 GW and the total capacity in the world was estimated close to 230 GW [31]. This would equal to 25 % growth compared to 2014. China has been one of the fastest growing markets in recent years. In 2015 a total of 15 GW was installed in China only. Germany has been the leader in Europe but UK took the place in 2015 with 3,5 GW installations. The markets show high variations. Countries which used to grow a lot have stalled due fading feed-in tariffs and higher regulations. Italy for example installed

“only” 300 MW of PV systems in 2015 compared to 9,3 GW in 2011. Spain and Belgium markets have also been on a downward trend. [31].

The direct conversion of solar energy into electricity is based on a phenomenon called photovoltaics. Essentially an electron absorbs energy from a photon and is able to move to valence band, leaving behind a free electron band called conduction band. Photon’s energy is converted into potential and kinetic energy of electrons. The electron absorbs the entire quantum energy of the photon defined as the product of Planck's quantum and the photon frequency [28, p. 234]

𝐸 = ℎ𝑓 = ℎ^𝑐

𝜆 (3)

where h = Planck’s constant (6,6256*10^-34 Js) f = frequency of the light [1/s]

c = speed of light (3*10⁸ m/s) λ = wavelength of the light [m]

The energy gap between the valence band and conduction band is called a band gap. This energy gap equals the minimum amount of energy required to transfer one electron from the valence band into the conduction band.Semiconductors have relatively narrow energy gap [28, p. 231]. When two types of semiconductors are connected together, for example, p- and n-type, the valence and conduction band create a voltage difference across the combined

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material, which is called the p-n junction. P-type semiconductor is called acceptor, meaning there is a shortage of electrons and n-type semiconductor is called a donor with a surplus of electrons. These differences are made with doping the material, sort of contaminating the structure with other material. The solar radiation maintains this excitation of electrons and the effect is continuous. A solar cell consists a thin layer of p-type semiconductor layer on a thicker layer of n-type semiconductor. [27, 32].

Due the fact that light comes with different wavelengths, it has different energy levels. The longer the wavelength the lower the energy. Basically solar cells efficiencies depend on how

“well” the cell utilises the full spectrum of light. This highly depends on the material the solar cell is made of as different materials have different energy gaps. The Figure 4 represents the theoretical efficiencies of different, single material solar cells under average conditions. The efficiencies are usually given in the Standard Test Conditions (STC), radiation of 1000 W/m², temperature of 25 °C and air mass off 1.5. The power generated in these conditions is referred as peak power, given in Wp [28, p. 243]. The efficiency can be improved by combining different materials and using multijunction cells. The most common material used in solar cells is the crystalline silicon.

Figure 4. The theoretical efficiencies of different solar cell material [28, p. 242].

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3.3 Hydro power

Hydro power is one of the oldest technologies used in the power production. In 2013 hydro power covered approximately 2.4 % of the world’s primary energy supply [33, p. 6]. In global electricity production its share is approximately 15 % [34, p. 17]. China is the world leader in hydro power production with a total of 319 GW installed capacity while the global installed capacity is approximately 1212 GW. The total installed capacity increased about 34 GW in 2015 of which China’s share is 19 GW. These numbers also include pumped hydro storages. United States, Brazil and Canada are the next in the line with the highest amount of installed capacity; 101 GW, 91 GW and 79 GW respectively. Finland’s installed capacity is approx. 3 GW. [35, pp. 4, 78]. In Finland the hydro power share in the total energy consumption is approx. 4 % while in the electricity production it covers approximately 20

% [36, 37]. However, there are only little left to improve in Finland in this matter. According to Motiva, most of the untapped rivers are less likely to be harnessed for conservation reasons but still estimate a total of 600 MW of potential increase [38].

Hydro power is very flexible in terms of power output. There is a merit why it is the most used storage method in the world (see chapter 3.7). Hydro power plants may adjust their production within seconds. Other advantages are the relatively cheap and mature technology while the barriers are related to the environmental or social aspect. Especially construction of dams usually causes the upper reservoir area to be flooded and possibly a whole communities have to be displaced. The dam failure is another risk to be evaluated. [27, p.

319].

Hydro power is essentially utilisation of running or falling water. The potential energy is converted into electricity. Hydro power should not be mixed with other water resources such as wave or tidal power. The hydro power through a turbine can be calculated with the following equation;

𝑃 = 𝜂_T𝑞_v𝜌𝑔Δℎ (4)

where P = power [W]

η = efficiency of the turbine

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qv = volumetric flow [m³/s]

ρ = water density [kg/m³]

g = acceleration of gravity [m/s²]

∆h = the height difference of the upper and lower reservoir [m]

3.4 Biomass conversion

Biomass can be utilised in many ways in the energy system. It can be used directly as fuel for combustion or conversed into different products with different conversion methods.

There are several conversion methods available and the process is chosen based on the raw material used. The conversion methods are roughly divided into two categories, thermochemical and biochemical conversion processes. Thermochemical processes are such as pyrolysis, gasification, torrefaction and direct combustion. These require high temperature and sometimes high pressure. The most used biochemical conversions are anaerobic digestion and fermentation. These conversion methods are introduced in their respective chapter. [39, pp. 4-6].

Biofuels are usually divided into 1^st, 2^nd and 3^rd generation based on the raw material they use. 1^st generation biomass resources compete with food generation in terms of land use and the raw material. The raw material used are such as corn, wheat, sunflower, rapeseed, soya bean, sugarcane and sugar beet which all are used in food and feed industry. 2^nd generation biofuels do not compete with the food crops and they’re based on waste residues from municipal, industrial and agricultural processes. The raw materials are for example sewage sludge, lignocellulosic waste materials from wood industry, energy crops, and animal residues. Energy crops however need arable land to grow and there is a debate whether fallow land is enough or will the energy crop cultivation compete with food production. 3^rd generation biofuels are based on seaweed and algae. The third generation biofuels are still a work in progress and not in commercial use. [39, pp. 4-6].

3.4.1 Thermochemical conversion

Thermochemical biomass conversion processes occur in high temperature and sometimes in high pressure. Direct combustion, gasification and pyrolysis are examples of

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thermochemical processes which convert biomass into heat or other energy carriers. Direct combustion process is not discussed in detail as it is considered to be widely known. The main feedstock for thermochemical conversions are wood based biomasses due the lignin content which is hard to process biochemically.

In pyrolysis process the biomass is conversed into the products in a high temperature and oxygen free condition. The process involves rapid heating of the feedstock which usually happens in a gas burner. The feedstock is converted into condensable and non-condensable gases, liquids and solids. There are different pyrolysis processes based on the temperature and the rate of the heating (Figure 6). The temperatures of pyrolysis processes vary from 300 °C up to 700 °C. Different products can be acquired with different processes. Liquid products include water, hydrocarbons and tar, gaseous products are such as carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ethane (C2H6), ethylene (C2H4) and solid product being mainly charcoal. Most of the products can be used directly either as a heat source, fuel or they can be upgraded to more valuable fuels. [39, p. 17] [40, pp. 149-151].

Figure 5. An example of pyrolysis process [40, p. 151].

Torrefaction is process which occurs in an absence of oxygen but in a lower temperature than pyrolysis. However, [39] considers torrefaction being a slow pyrolysis process.

Torrefaction temperatures varies from 200 °C up to 300 °C. Torrefaction process produces mainly solids and gas products. The main difference of torrefaction and pyrolysis is that the liquid production in pyrolysis process is maximised, whereas in torrefaction the energy

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content of the fuel is increased by increasing carbon content and decreasing oxygen and hydrogen content. [40, p. 89].

Figure 6. The differences between the pyrolysis processes [39, p. 19].

Gasification is a process where the raw material is conversed into gas, whereas pyrolysis and torrefaction products are mainly liquids and solids. Pyrolysis and torrefaction occur in an absence of oxygen but gasification requires a gasifying medium, often air but oxygen or steam are also used. The medium reacts with solid carbon and hydrocarbons and converts them into syngas, containing mainly CO and H2. Depending on the medium, the syngas heat value ranges from 4-28 MJ/Nm³. Gasification also happens in a higher temperature, usually between 600 °C to 1300 °C. The gasification process usually follows the stages represented in the Figure 7. [40, pp. 199-202].

Predrying or heating is important in all thermochemical processes as biomass moist content may vary from 30 % to 60 %. The energy needed to remove the water from the biomass is estimated to be 2,2 GJ/kgH2O and this energy is unrecoverable. The final drying happens in the gasifier. In pyrolysis stage more char is formed as large biomass hydrocarbon molecules break into smaller gas, liquid and char molecules. In the last gasification stage, the gasifying medium and char reacts and converts into carbon monoxide and hydrogen. There are no clear boundaries between these stages and they often overlap. [40, pp. 201-204].

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There are several types of gasifiers in use. In updraught gasifier the air intake is at the bottom as the figure 7 shows. The advantages of updraught gasifier are simplicity, high charcoal burn-out and internal heat exchange leading to low exit temperature for gases and high system efficiency. In downdraught gasifier, the intake of air is in lower section of the gasifier and the product gases are gathered from the bottom of the gasifier. This leads to reduced tar contain in the product gas. Downdraught gasifier however can not operate with as diverse feedstock as updraught. The up and downdraught gasifiers are called moving bed gasifiers in general. [39, pp. 102-104]. Fluidized bed reactors are also used in gasification. The reactors are either bubbling or circulating depending on the velocity of the inlet air. The bed consists of solid particles which heats the feedstock quickly to the bed temperature which ranges from 800 to 1000 °C. In the bed, the feedstock goes through rapid drying and pyrolysis producing gases and char. The fluidized beds can operate with wider range of feedstock and mixture. [40, pp. 214-216].

Figure 7. Different stages of gasification process and chemical reactions in them [40, p. 213].

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3.4.2 Biochemical conversion

Examples of biochemical processes are fermentation and anaerobic digestion. These are very different processes with different feedstock used and end products. Biochemical processes usually require long residence time.

Anaerobic digestion uses organic wastes, agricultural and municipal residues, animal manure and sewage sludge as a feedstock to produce biogas through biochemical process.

The process is based on the decay of the organic material in an absence of oxygen. There are few key stages in the decaying process. The digestion starts with a hydrolysis, where polymers are broken into smaller parts such as sugars, amino and fatty acids. These hydrolysis products then decay volatile fatty acids in acidogenesis. Further digestion is called acetogenesis, where molecules from acidogenesis are turned into acetic acids and CO2 and H2. Final stage of the digestion is called methanogenesis. Last stages utilise the products from previous stages and convert them into methane and carbon dioxide, which are the content of the end product, biogas. [39, pp. 110-112]. Biogas mainly consists of CH4 (55–

75 %), CH2 (25–45 %) and small amount of CO, H2 and N [41, p. 3]. The digestion process is very sensitive to the condition it is occurring. The optimum pH value is usually between 6,5–7,5 [42, p. 25].

There are different configurations of the digestion process, whether it is a batch or continuous, mesophilic or thermophilic, what is the solid content or whether it is single or multistage. Mesophilic process happens in a temperature of 35-38 °C and thermophilic process in 50-60 °C. Higher temperature generally means faster reactions and faster gas yields but increased energy demand. Solid content means whether the feedstock is dry or wet. The one stage system is a reactor where all the different digestion stages happen with less control of the reactions. In a multistage the three first stages usually happen in a same reactor (hydrolysis, aceto- and acidogenesis) and the methanogenesis system have different vessel. This is for maximising the control over the conditions in the process. [39, pp. 113- 116].

Fermentation is an old and well known process of making alcohols such as ethanol. The feedstock is usually containing sugars, such as glucose, fructose and sucrose. Sugars react with yeast used in the process to form ethanol. The fermentation product usually contains

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little ethanol so it has to be further distilled. New fermentation processes are under development especially with different feedstock. As sugary plants such as corn, wheat, and sugarcane are used in food industry, lignocellulosic biomass is more convenient feedstock for fermentation. The lignocellulosic fermentation however is a lot more complex than fermentation of sugars. These lignocellulosic materials need to be broken down into simple sugars before the fermentation or distillation. This can be achieved by using either acid or enzyme hydrolysis. [43].

3.4.3 End products

In gasification process the end product is a syngas containing mainly CO and H2. In pyrolysis the focus is in the liquid end product, called pyrolysis oil. Torrefaction end product is charcoal or bio coal. Anaerobic digestion is producing biogas containing mainly CH4 and CO2 and fermentation end product is ethanol. Most of these end products can be used as a fuel themselves for electricity and heat production. Some of them can be upgraded to more flexible and valuable fuel for transportation.

There are several pathways for the upgrading of syngas, biogas or CO2. Upgrading could be done for example with Fischer-Tropsch synthesis, which is an old technology used to produce liquid fuels such as biodiesel. Upgrading could mean other chemical synthesis as well such as methanation or hydrogenation of different syngases to SNG (synthetic natural gas). Biogas usually contains approx. 50 % of the CO2 which in most cases have to be cleaned. While the CH4 can be used directly, CO2 could be synthesised with hydrogen to produce more CH4. Gasification syngas can be treated the same way.

3.5 Combined heat and power

The share of the CHP (combined heat and power) plants in Finland is one of the top tiers in the world. The combined energy production is utilised in industry and district heating. The share of CHP in the electricity production has been close to 34 % for the whole country. The CHP production divides into district heating and industrial CHP, with a share of 60 % to district heating facilities. [37].

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By combining heat and power production, the energy content from a fuel can be utilised more efficiently. Compared to condensing power, which efficiencies may vary from 30 % to the highest 60 % in CCGT (combined cycle gas turbine), CHP plants may have a total efficiency close to 90 %. Heat may be utilised in couple ways in a CHP plant. It can either use bleeder or back pressure turbines. Bleeder turbines are more common when the steam is used in a process and certain pressure is required. Back pressure mode is like a regular condensing plant except the heat is utilised through heat exchanger. The boiler technologies used in the CHP plants are not discussed in detail but the most common boilers are FBB (fluidized bed boilers) or grate boilers depending on the fuel used. Gas turbines and engines are also used in CHP production.

3.6 Heat pumps

Heat pumps use in the world has grown significantly in the last few years. In Finland alone, more than 730 000 heat pumps are already installed with an increase of 60 000 heat pumps in 2015 [44]. The heat or cooling energy adds up to 5 TWh per year with the capacity.

Implementing cooling increases the cost efficiency of the installation. In Helsinki, a heat pump plant is producing district cooling and heating from recovering heat from sewage water and the return water of the cooling grid. The heat pump plant’s district heating capacity is 90 MW and 45 MW of cooling capacity. It is considered to be the largest heat pump plant in the world. [45].

The principle of heat pumps is similar to refrigerators. The Figure 8 represents a principle of a heat pump. Generally speaking, a heat pump consists of four main components;

evaporator, compressor, condenser and expansion valve. A refrigerant (a medium used in the circulation) circulates in a closed circuit and the whole process base on the refrigerant’s phase change. The refrigerant absorbs heat from the heat source and evaporates at low temperature and pressure in the evaporator. Compressor increases the pressure and the temperature of the vaporized refrigerant to the required level. The refrigerant then transfers into liquid again in the condenser where it rejects the heat. The expansion valve changes the high pressure liquid back to low pressure liquid to be evaporated again in the evaporator.

The most common refrigerant used nowadays is the R-410A, however due refrigerants being

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harmful to the ozone layer new refrigerants are in development. The natural refrigerants used are such as ammonia, hydrocarbons and carbon dioxide. [46].

Figure 8. Principle of a heat pump [46].

The possible heat sources for heat pumps are such as the air, ground or water. Outdoor air heat pumps are one of the most common heat pumps. Heat recovery from the exhaust air is also raising interest as the air flow is directly related to the space heating demand. The ground heat source is utilised with a vertical borehole system or with a horizontal heat transfer fluid circuit. The circuit is installed quite shallow where as the borehole system is drilled vertically on the ground, up to 200 meters. Water could also be utilised, mainly recovering the heat from industrial or municipal waste water. As the waste water is warmer than natural water resources, they could be used for district heating production as well. Heat pumps may heat the indoor air or they can be used for heating the hot water. The heat pumps may be referred as air-to-air or air-to-water heat pumps. [46].

Heat pumps efficiency is often referred as the coefficient of performance (COP). COP generally shows how much heat energy is produced with a certain amount of electricity.

Another factor called Seasonal Performance Factor (SPF) is used to inform about the annual performance of a heat pump. The COP may be as high as 5 for the new heat pumps where as the SPF during a whole year is closer to 3. The temperature difference between the heat sources is a major factor in the heat pump performance.

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3.7 Energy storage

Energy storage in the future energy systems is crucial in order to integrate the fluctuating renewable energy production into the system. As the production and demand balance has to be equal in the system, the new renewables require the flexibility from the whole system.

The energy storage does not only apply to the electricity as it can be stored many other ways as well. The storages should cover all the different networks; gas, heat and electricity. The technologies are already here such as the pumped hydro energy storage (PHES), batteries, thermal storages, compressed air energy storage (CAES) and other power-to-gas (PtG) technologies. Power-to-x (PtX) is concept of storing electricity as other energy carriers in general. The Figure 9 represents the current technologies with capacities, response times, efficiencies and other features.

Figure 9. Some properties of different energy storage methods [47, p. 135].

According to [35], the PHES accounts for over 97 % of the world’s energy storages. The principle of PHES is based on very traditional and well known technology of conventional hydro power. Pumps are used to pump water into higher reservoir during time of excess electricity. During peak load times or high demand times the reservoir is then emptied through water turbines, generating electricity. This is very mature and easy way of storing

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energy. It is not restricted to excess electricity and with a smart control system the pumps can be run in low-cost times and then storage emptied during high-cost times. Typically, the PHES system is constructed with a single penstock, meaning it can either charge or discharge, not being able to do both simultaneously. It might be beneficial to construct double penstock systems where the system can use pump and turbine at the same time. This brings more flexibility to the storage and possibly aids integrating more renewable energy.

For example, the pump can be used during excess electricity production from wind or solar power while the turbine can be used as grid stabilising power at the same time. Also the storage capacity won’t fill up as easily so smaller capacities (size) could be built. [48, p. 39].

Other possible energy carriers are gases and they’re utilised with so called PtG technologies.

CAES for example uses compressed air for storing energy. Electricity is used to run a compressor to pressurise air. During peak loads the air can be then released through gas turbine to produce electricity. The storage could be a geological formation such as underground salt caverns, depleted oil wells or underground aquifers. [49, p. 42]. The natural formations could be utilised as thermal storages as well. The most common liquid used in thermal storing is water.

Hydrogen is seen to have a major role in future energy system. It can be used directly in fuel cells to produce electricity or it can be used as a syngas in synthetic fuel production. It is also used in industry for various processes. This leads to an interest to store excess electricity as a hydrogen. Today hydrogen is mainly produced from methane in steam reformation.

However, a more attractive method of producing hydrogen is via water electrolysis. It is more expensive but the feedstock, water, is more available and the hydrogen is purer. [50, pp. 100-102]. There are several electrolysers which are based on different reactions. The most common electrolyser is alkaline electrolyser which is based on the following reactions

2OH⁻ →¹

2O₂+ H₂O + 2e⁻ (anode) (3) 2H₂O + 2e⁻ → H₂+ 2OH⁻ (cathode) (4)

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The OH ions oxidise in the anode and release oxygen, water and electrons. The cathode gains electrons and release hydrogen and OH ions. [32, p. 38]. The hydrogen is usually pressurised or liquefied for storage use.

Battery technologies are highly debated topics in the energy storage, especially the costs.

The previous Figure 9 shows the costs of different technologies including battery technologies. The development seems to focus on finding new materials and combinations such as the advanced lead-acid, lithium-ion and flow batteries. Battery technology will be essential when the share of the electric vehicles increase and the demand for new, recyclable batteries increase. The interest in electric vehicles may give boost to the development battery technologies and vice versa. Electric vehicles themselves could be used as electricity storage when Vehicle-to-Grid (V2G) technology gains more maturity. [51].

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4 ENERGY SYSTEM OF SOUTH KARELIA

This chapter is a brief introduction to the energy system in the region which is later modelled in the thesis. This chapter introduces the whole energy palette even though the models will leave out the industry. It may be beneficial to identify the magnitude and importance of the industry as well in the region.

The region of South Karelia is one of the Finland’s nineteen provinces. There are nine rural districts in the area of which two are cities, Lappeenranta and Imatra. The population of South Karelia is approx. 131 000 [52]. The focus of this chapter is on the energy production and consumption, however the individual heating and transportation are represented in chapter 6 as there are more assumptions in them. South Karelia is already the number one province in renewable energy usage in Finland. This is due the heavy wood industry and the large hydro power plants in the region. The share of renewables in the PEC (primary energy consumption) is almost 90 % as seen in the Figure 10 [53].

Figure 10. The share of renewables in South Karelia compared to whole Finland. Edited from [53], data available from [36].

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4.1 Energy production

The electricity in South Karelia is mainly produced in hydro power plants and CHP plants in industry. In the Figure 11 is represented the province’s electricity production between 2007 and 2014. The electricity production has been around 4 TWh/year in total in the last years and the differences in each year are mainly due the available hydro power. It is clear the industrial CHP and hydro power are major factors in the regional electricity production.

CHP in district heating and condensing power are only marginal (400-500 GWh in total) in the power production. The first wind mills started producing electricity in 2013. The installed capacity of the wind farm is 21 MW

The hydro power is produced in Fortum Oyj hydro power plants in Imatra. The company has two power plants, Tainionkoski and Imatrankoski. The capacity of the Tainionkoski power plant is 63 MW and the Imatrankoski power plant is the Finland’s biggest hydro power plant with capacity of 195 MW. There was a recent increase in the capacity in Imatrankoski as the capacity was raised from 178 MW to 195 MW. [54].

Figure 11. Electricity production in South Karelia between 2007 and 2014 [37].

The industrial CHP consists mainly the power plants in the wood industry. There is a power plant register in which one may find the region’s industrial power plants and their capacities

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5

2007 2008 2009 2010 2011 2012 2013 2014

TWh

Hydro power Wind power Industrial CHP CHP district heating Condensing

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[55]. The power plants are listed in the Table 1 with their location and capacities. The total industrial CHP capacity is 354,8 MW. UPM-Kymmene Oyj, Stora Enso Oyj and Metsä are all big wood industry companies in Finland and known world-wide. FC Power is a company owned by Leppäkosken Sähkö Oy and Kemira Chemicals Oy and it is located in Joutseno.

FC Power uses hydrogen as a fuel for the district heating [56].

Table 1. Industrial CHP in South Karelia [55].

Company Location (plant) Capacity [MW]

UPM-Kymmene Oyj Lappeenranta 93,6

Stora Enso Oyj Kaukopää 134

Stora Enso Timber Oy Ltd Honkalahti 3,8

Metsä Fibre Oy Joutseno 85

Metsä Board Oyj Simpele 34,5

FC Power Joutseno 3,9

There is only one condensing power plant in South Karelia [55]. This is owned by Lappeenrannan Energia and it is located in Mertaniemi. The power plant is nowadays rented for Fingrid Oy and it is used for frequency restoration reserve for the electricity grid. There have been changes made in the power plant as Lappeenrannan Energia changed the old boilers, electricity and automation systems and flue gas duct. A total of 130 MW of district heating reserve capacity was removed and 80 MW of DH capacity was installed [57]. Being in a frequency restoration reserve mean the power plant is not used for commercial electricity production purpose [58].

Most of the district heating CHP is produced by Kaukaan Voima’s biopower plant. The power plant was built in 2013 and it is producing process heat for the UPM biofactory in Kaukaa and also district heat and electricity for Lappeenrannan Energia. Kaukaan Voima is producing approximately 85 % of the district heating demand in Lappeenranta. The thermal capacity of the CHP plant is 262 MW. The electrical capacity of the plant is 125 MW [59].

There is also a CHP plant in Imatra owned by Imatran Energia.

Heat for district heating is also produced in separate heat plants. The Finnish Energy has a statistic of all the boiler plants in Finland. There are a total of 600 MW of district heating capacity in South Karelia of which approximately 365 MW are separate heat plants. All the

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district heating producing plants are represented in the appendix 1. In Figure 12 is shown the district heating production and consumption from 2009 to 2014 in the province. A more detailed discussion of the district heating system is in the reference scenario introduction in chapter 6.

Figure 12. DH production and consumption in 2009 to 2014 [60].

4.2 Energy consumption

There has been a downward trend in the electricity consumption in the region (Figure 13).

This may be due increase in energy efficiency or a slight decrease in the industrial production volume. The electricity consumption has been over 5 TWh. Most of the electricity is consumed in the industry in the area, around 85 %. The rest is the electricity is consumed in living and commercial purposes.

0 100 200 300 400 500 600 700 800 900 1 000

2009 2010 2011 2012 2013 2014

GWh

Year

Net production Consumption

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Figure 13. Electricity consumption in different sectors in South Karelia from 2007 to 2014 [61].

In Figure 14, is shown the different industry sectors and their electricity consumption. The wood industry is the biggest electricity consumer in South Karelia. The 2^nd largest consumer is chemistry. Electricity consumption is in a downward trend in the industry as seen in the figure. There is only a slight increase in 2014. This could be due the overall economic situation of the wood industry.

Figure 14. Electricity consumption in industry [62].

0 1 2 3 4 5 6 7

2007 2008 2009 2010 2011 2012 2013 2014

TWh

Living Industry Services

0 1 2 3 4 5 6 7

2007 2008 2009 2010 2011 2012 2013 2014

TWh

Mining Food industry Clothing industry

Wood industry Chemical indusry Metal processing

Machines and metal products Electronics and electric industry Other manufacturing

Renewable energy scenarios for South Karelia – non-industrial energy demands