6. VALIDATION OF THE RESULTS
6.3 Profitability calculation
The appropriateness of the established schedule can be estimated by calculation of its profitability. First of all, it is necessary to calculate the cost of the battery work per cycle.
According to [33], the LiFePO4 battery will reach 80% SOH after approximately 3000 FEC with 100% DOD. In [46] it was pointed out that the round trip efficiency of LiFePO4 battery is 98%. In addition, the authors noted the variable battery price is 752 β¬/kWh.
60
45
Therefore, the total amount of cycles over the lifetime is:
2 β ππ π β πΆ π·ππ·(100%) β πππ£,ππ¦ππππ = πππ‘ππ π π‘ππππ ππππππ¦ (2) The investment cost of the BESS is calculated by the next formula:
πΆππ π‘πππ‘π‘πππ¦β πΆπππ‘π‘πππ¦= πΆππππ₯ πππ‘π‘πππ¦ β¬ (3)
The price of the battery work per 1 kWh is
πΆππ π‘1ππβ= πΆππππ₯ πππ‘π‘πππ¦ β¬
πππ‘ππ π π‘ππππ πΈπππππ¦= 0.13 πβ¬
ππβ, (4)
where
Ι³RT round trip efficiency
CDOD(100%) capacity with a DOD = 100%,
Nav.cycles the average number of cycles
Costbattery cost of the battery
Cbattery battery capacity
Since the amount of charging or discharging energy was assumed as permanent for Elspot and Elbas market, it is necessary to calculate the cost of one discharge or charge event:
19.8 ππβ β0,13β¬
ππβ = 2.57β¬
For FCR-N market, the battery cost is calculated by other way. Firstly, the changing of batteryβs SOC needs to be defined:
πππΆπ‘β πππΆπ‘+π = βπππΆ (5)
Secondly, changing of capacity regarding every change of SOC is calculated:
|βπππΆ β πΆπππ‘π‘πππ¦|
100 = βπΆ (6)
Then, sum of the capacity change for one hour is considered:
β βπΆ = βπΆ1 βππ’π (7)
Finally, the operation cost of one hour of work on FCR-N market is defined as:
βπΆ1 βππ’πβ πΆππ π‘1ππβ = πΆππ π‘1β (8)
46
Consequently, the revenue from all the markets was calculated and presented at Table 3.
Table 3. Calculation of the revenue flow during the battery operation, 6.12.2018
Time Type of the market Allocated capacity, kW; kWh Market price, β¬/MWh; β¬/MW Battery cost, β¬ Market revenue, β¬ Revenue, β¬
5:00
47
As it can be seen from the table, the revenue for one day of battery work amounts -30.27β¬.
Further, the same calculation was conducted for another two days (Table 4).
Table 4. Calculation of the revenue
Date Revenue, β¬
7.12.2018 -38
8.12.2018 -30.71
Eventually, according to the results of the tests all three days brought a negative profit. It is worth to note that the chosen hours of work on Elspot and FCR-N market in majority were the most profitable. During three days, 8:00 and 9:00 on Elspot market were the most profitable during the morning or even during the all day. In the future, the chosen hours are needed to be selected every day with accounting of various details.
It is worth to note that during the calculation, the cost of the contracts concluded with TSO and Nord Pool were not considered. Furthermore, the tests with a real battery were conducted in November and December of 2018. The profitability of the battery will drastically increase at the period from April till September. The growth of power output of the PV panels will lead to reduction of Elbas market as energy source for charging the battery.
48 7. CONCLUSION
The Masterβs thesis presents the decision-making simulation tool imitating artificial work of the BESS on the electricity markets. The battery implements several tasks: supply of energy to Elspot and Elbas markets and work for the market of ancillary services β maintenance of frequency stability. For the battery charging, SPPs installed on the university base were used as a main energy source. If the power production of the PV panels is low, Elbas market was applied for the battery charging. The battery operational schedule was settled on the base of historical data. Coincidence of peak hours for the last year was calculated for Elspot market and FCR-N market. Then, these hours were settled for the operating schedule. Left hours were established for work on Elbas market. The simulation tool was developed by use of Python.
Operation of BESS implies many parameters that cannot be predicted or calculated in advance. For this reasons, parameters such as battery degradation were neglected. The amount of provided or absorbed power was established as permanent.
Eventually, the simulation tool demonstrated its efficiency and proved the ability of BESS to work during the day. The energy was supplied to the priority markets at the morning and at the evening. In addition, the energy was also provided to the hourly market. During the day the battery was successfully charged either from the SPPs or from Elbas market.
After the tests of artificial battery, validation of obtained results was done with a real LiFePO4 battery. The line of the tests approved determined operational schedule. Also, it is shown that the estimated value of SOC change for 1 hour approximately matched the real one. The slight deviation could be explained by a number of terms such as battery degradation rate, number of cycles, temperature and others. Therefore, in further studies batteryβs SOH is needed to be taken into account. In addition, the yield of the project for the owner was calculated. The calculation did not consider cost of the contracts concluded with Nord Pool and TSO. Eventually, according to the results, work of the battery in the framework of the chosen strategy is not profitable. It is worth to note that the tests were conducted in November and December. During the summer period the profitability will increase due to replacement of charging from Elbas market by use of SPPs.
There are a lot of open questions regarding the use of BESS as energy source. Besides it, BESS installed in the residential sector can also be used for the grid needs. At the current
49
moment, the cost of the BESS is one of the main issues that inhibits their high penetration to the market due to absent of profitability. It is worth to note that the cost reduction and sufficient support from the government will positively effect on their distribution. Their application for both β the owner and the grid β will impact towards sustainable work of the electrical grid, increasing of ownerβs profit, penetration of renewable energy sources and development of distribution generation.
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56 Appendix A. The reserves products [38]
Market place Contract type Minimum
bid size Market gate closure Frequency of use Price level 2018
FCR-N Hourly market 0,1 MW Yearly market previous autumn,
hourly market day before at 18:30 Several times a day 14 β¬/MW,h (yearly market)
FCR-D Yearly and
hourly markets 1 MW Yearly market previous autumn, hourly market day before at 18:30
Several times per day - per year
2,8 β¬/MW,h (yearly market)
aFRR Hourly market 5 MW Day before at 17:00 Several times a day
Hourly market price + balancing energy
price Balancing power
market (mFRR) Hourly market 5 MW 45 min before each hour According to the bids,
several times/day - per year Market price Balancing
capacity market (mFRR)
Weekly
auctions 5 MW Week before
on Tuesday at 12:00
According to the bids,
several times/day - per year ~3 β¬/MW,h
57
58 Appendix C. Proposed scenario of act
Time Market 1 SOC1, % Action 1 Market 2 SOC2, % Action 2
00:00 65 Standby mode 65 Standby mode
01:00 65 Standby mode 65 Standby mode
02:00 65 Standby mode 65 Standby mode
03:00 65 Standby mode 65 Standby mode
04:00 65 Standby mode 65 Standby mode
05:00 FCR-N 65 Discharge FCR-N 65 Charge
06:00 FCR-N 50 Discharge FCR-N 80 Charge
07:00 35 Standby mode 95 Standby mode
08:00 Elspot 35 Discharge Elspot 95 Discharge
09:00 Elspot 20 Discharge Elspot 80 Discharge
10:00 PV/Elbas 5 Charge 65 Standby mode
11:00 PV/Elbas 20 Charge Elbas 65 Discharge
12:00 PV/Elbas 35 Charge 50 Standby mode
13:00 PV/Elbas 50 Charge Elbas 50 Discharge
14:00 65 Standby mode 35 Standby mode
15:00 Elbas 65 Discharge Elbas 35 Discharge
16:00 50 Discharge 20 Standby mode
17:00 Elbas 50 Standby mode Elbas 20 Discharge
18:00 Elspot 35 Discharge Elspot
Penalty 5 Standby mode
19:00 Elspot 20 Discharge Elspot
Penalty 5 Charge from
Elbas
20:00 Elbas 5 Charge Elbas 20 Charge
21:00 Elbas 20 Charge Elbas 35 Charge
22:00 Elbas 35 Charge Elbas 50 Charge
23:00 Elbas 50 Charge Elbas 65 Charge