Residential energy storage using Lithium-Ion batteries
We are faced with many problems due to uncertainty that is prevailing in the country with regard to continuous power supply. Many of us are wondering whether there will be power cuts in the near future, due to lack of rain for hydropower generation and coal and fossil fuel to generate thermal energy. One solution to the above problems will be to deploy residential Energy Storage Systems (ESS) where we store energy generated from solar systems during the day in batteries and use stored energy at night. While this is feasible and practiced world over, how feasible is it in Sri Lanka?
The concept of storing solar energy in residential battery storage and making use of stored energy when solar energy is not available is referred to as “Solar Self-Consumption” (SSC). It is an economical way of making use of free energy from the sun. This is extremely rewarding in a tropical country such as Sri Lanka as we enjoy sunlight throughout the year. However, the only constrain that may hinder large scale SSC adoption in the country is the high cost of Lithium-Ion battery, which is mandatory for an efficient ESS.
In order to mitigate the high cost of Lithium-Ion battery, we could use a proven Energy Storage Management System (ESMS) and make use of the battery to generate an income. This will allow us to recover the cost of the battery, throughout the life span of the battery. Most Lithium-Ion batteries available today are with a life span of 7-10 years if the battery is used carefully and according to manufacturer’s recommendation.
A typical battery bank for an average house which consumes up to 600 units per month will be 5.12 KWh. With the manufacturer’s recommended Depth of Discharge (DoD) of the battery, which is 80 per cent, we will be able to use 4 units per day, discharged from the battery at night. If we plan to use this energy during peak hours, between 6.30 pm to 10.30 pm, we will be able to save a considerable amount per day. In addition, we will enhance our saving, if we charge the battery using low-cost energy at night, between 22.30 and 05.30 next morning and use that energy between 05.30 and 07.30 next day.
According to the above calculation, we will be able to save over Rs. 650,000 in seven years, which is the standard life span of the battery. Therefore, this saving will cover the cost of battery replacement in seven years and leave us with a net income from using stored energy form the battery. If we are able to use the battery for 10 years by carefully managing the battery, we will be able to make a handsome profit of over Rs. 500,000 in seven years from the battery, which is quite attractive to any consumer. In addition, the consumers will be encouraged further to deploy SSC at their cost, if they are paid at a higher price for energy exported during evening peak, at least Rs.46 per unit. This will further reduce the burden of the Ceylon Electricity Board (CEB) during evening peak.
If adopted by a large number of households in Sri Lanka, SSC will be a viable solution to current energy crisis, where power cuts seem necessary for CEB to manage peak load. Also, consumers will be able to use stored energy instead of gas during morning and evening peak hours for their day to do activities such as heating water, cooking and baking etc. As we understand, recent heavy electricity usage by consumers due to the gas shortage and the fear of using gas for cooking, affected the peak power demand of the country where the power regulator (PUCSL) had to request consumers to use power for cooking during off-peak times. SSC is a definite solution to this problem and the Government should support the adoption of SSC by the consumers with incentives and duty waivers for Lithium-Ion batteries as well as rewarding consumers for their exported energy during evening peak.
The SSC model I have described has been used in my house since July 2020 and it is the first system I manufactured, before I stopped all my operations due to COVID-19 pandemic. Therefore, the concept is proven and it is working for me as follows; a) I have 4.2KWp solar on my roof but I am not exporting to the grid – so I do not have a contract with the power distributor; I am using 50-60 per cent of energy I am using per month from my SSC (my capacity is limited to 2.4KWh battery I have deployed) and that is the maximum I can achieve. My bill has reduced from Rs.15,000-18,000 per month to Rs.4,000 per month; We have started using electricity for cooking, heating water etc, reducing the use of gas.
I have applied for a patent for my technology and it is pending. What I need is an O&M company that believes in the technology and the software platform I have developed and which I am using successfully, to market it professionally with required after sales support.
(Jeremy Fernando MIET (UK), is the Managing Director Innovative Smart Solutions (Pvt) Ltd), who revels in innovation in renewable energy for progress. He can be reached at jeremyf@smarthome.lk).
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