University:
Conestoga College
Course:
ERGY8070 | Energy, Storage and Management
Academic year:

2021
Views:

169

Pages:

2
Author:

S T Cherukuri

Week 5 ERGY8070 Battery Storage Practice Problems #2 1. Name one advantage that Lithium Ion and Lead Acid batteries have over each other. 2. A lithium ion battery system has usable storage capacity of 25 kWh. If the system has a maximum depth of discharge of 85%, what is the total storage capacity of the system? 3. A battery system provides 75 kWh to an inverter, which provides 69.8 kWh to a building. What is the efficiency of the inverter? 4. When comparing two electricity generation options (e.g. wind, solar, combined cycle natural gas, etc.), should you always select the option with the lower LCOE? 5. A small pump house has a 4.25 kW pump. The pump runs for 4 hours per day. If a battery storage system has been sized for 2 days of autonomy for this pump, how much energy can it provide? 6. What is the difference between blue and green hydrogen? Week 5 ERGY8070 ANSWERS 1. Some advantages of lead acid batteries are: • Lower self discharge • Higher tolerance of overcharging • Higher peak C-rate • Lower price (first cost) Some advantage of lithium ion batteries are: • Longer cycle life • Higher depth of discharge • Superior energy density and specific energy !"#$% '( !)*+%,-." /% 2. energy storage capacity (Es) = !"#$% '( !)*+%,-."% The system’s usable storage capacity is 25 kWh and the max depth of discharge is 85%. Therefore: !"#$% '( !)*+%,-." /% 12 3/% energy storage capacity (Es) = !"#$% '( !)*+%,-."% = 3. 𝜂)78"-$"- = "7"-.9 ':$ (3/%) "7"-.9 )7 (3/%) = 4.62 =:)>?)7. "7"-.9 (3/%) =,$$"-9 *9*$"@ "7"-.9 (3/%) = = 29.4 𝑘𝑊ℎ AB.6 3/% C2 3/% = 0.93 = 93% 4. No. As per Week 5, slide 44, LCOE does not distinguish between dispatchable and non-dispatchable systems and does not include environmental externalities. LCOE is an important consideration, but it should not be the only factor. 5. The daily energy use of the pump (in kWh) is: Daily Energy Use = Power Draw (kW) x Daily Run Time (Hours) = 4.5 kW x 4 hours/day = 18 kWh Because the battery system is sized for two days of autonomy, it must provide enough energy for two days of the pump’s daily energy use. Therefore: Provided Energy (kWh) = Daily Energy Use (kWh) x Days of Autonomy = 18 kWh x 2 = 36 kWh 6. Blue hydrogen is made from fossil fuels, but the carbon emissions from the production process are captured and sequestered. There are however carbon emissions associated with the production of the fossil fuels used to create blue hydrogen in the first place. Green hydrogen is made from electrolysis using renewable electricity (e.g. wind or solar). Therefore, there are no carbon emissions associated with green hydrogen (other than the carbon emissions associated with the manufacturing of the wind or solar generation and electrolysis equipment).