In this TASK an energy storage for renewable system is analysed. A small town has invested to a renewable system including 20 MW wind farm and 10 MW solar power plant. A maximum power demand is 22 MW. Average diurnal power curves can be seen in the table 1. The plan is to close old thermal power plant and invest on the back-up battery power storage.

Table 1. Average hourly production and consumption during one day.

Hour	wind	solar	demand
0	10	0	6
1	12	0	5
2	14	0	4
3	14	0	4
4	15	0	4
5	15	0	5
6	14	0	6
7	10	1	8
8	8	3	12
9	6	6	15
10	6	8	18
11	5	9	20
12	4	10	21
13	2	9	22
14	2	8	22
15	1	6	21
16	1	3	20
17	1	1	18
18	2	0	16
19	3	0	10
20	4	0	8
21	5	0	7
22	7	0	6
23	8	0	6

A) Dimension an electrical storage, which quarantees the power supply during the 1 day conditions described in table 1. Assume, that the maximum state of discharge is 80% and the efficiency of discharge and charge is 98%.

Tip: Calculate the power needed from energy storage and integrate the energy needed from energy storage.

Maximum energy (minimum value of integral) deficit during day: (absolute value)

Answer MWh

.

Needed storage capacity

Answer MWh

.

B) Calculate needed C-number for charge and discharge.

C-number for discharge (absolute value)

Answer is

.

C-number for charge

Answer is