Photovoltaic (PV) power is becoming popular worldwide as an alternative to grid power for various reasons. It gives an energy independence and freedom, it helps reduce greenhouse gas emission and combat global warming, it helps people taking advantage of various Government subsidies and incentives, and it also generates some revenue by selling surplus power back to the grid. At the end of the period you own the system and claim depreciation and some tax benefits. All these compelling factors may motivate people to opt for PV solar power. But you should also do some math and make a cost benefit analysis to choose a right system for you.
When there is a good sunshine day after day and throughout the year, PV solar is good proposition and can be really rewarding. Unfortunately that is not the reality. There may be many cloudy, rainy and fogging days in a year and your PV solar capacity may be overestimated or underestimated. You know the real data only after one or two years of life experience. It is a long-term financial and ethical decision one has to make and the decision should be absolutely right. You can make such a decision by carefully examining all the factors, not just by looking at the first cost but looking at operating and maintenance costs and all the costs and benefits associated with them.
Storage batteries are inevitable in PV solar systems, especially for grid independent systems. Even with grid connected PV solar system the design and installation of a correct battery bank, controllers and rectifier are important issues. In this article we will discuss about grid independent system because many developing countries in Africa and Asia do not have 24×7 uninterrupted grid power supplies. Many people living in islands have to manage their own power by using diesel generators. This is the stark reality.
Let us assume that you design a system assuming a daily average power consumption of 25,000 kwhrs/day, which is suitable even for a medium size family in US. We made an optimum design study between two systems; first containing PV solar,battery,controller for grid independent power supply; and second system with PV solar, battery, water Electrolyzer,Hydrogen storage and PEM Fuel cell and a rectifier for grid independent system, based on the same power consumption of 25,000kwhrs/day. You can clearly see the difference between the two systems by the following data.This financial analysis was made assuming there is no Government subsidies and incentives.
Grid independent system with battery storage for 25,000kwhrs/day power:
Total NPV (net present value):$ 342,926
Levelized cost of energy: $2.94/kwhrs
Operating cost/yr: $22,764
Grid independent system with Hydrogen storage for 25,000kwhrs/day power:
Total NPV (net present value): $ 169,325
Levelized cost of energy : $ 1.452/kwhrs
Operating cost/yr: 8,330
The number of batteries required in the first case is 17 numbers. In the second case, number of batteries required is only 2.Obviously, the levelized cost of power using PV Hydrogen (storage) is less than 50% of the power generated using PV battery (storage) for the same energy consumption of 25,000kwhrs/day. The operating cost is only one-third for PV Hydrogen system compared to battery system. Batteries are indispensable in any renewable energy system but reducing their numbers to the lowest level is important, when the life of the system varies from 25 years to 40 years. The numbers and the cost of batteries and their maintenance cost will make all the difference.