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Tag Archives: Mains electricity

 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.

 

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Renewable energy industry has slowly but steadily started expanding in many parts of the world in spite of  high cost of investment and high  cost of energy. Countries like US, Germany and China are now investing on large-scale solar and wind technologies, opening new avenues for investments and employment opportunities. Many of these technologies will undergo several changes over a time before it can completely substitute fossil fuels. How long this process will take will depend upon number of factors; but the single biggest driving force will be ‘the issue global warming and its consequences” and also on uncertainties over oil reserves in the world. Nothing dramatic will happen in the near future except that the concept of alternative source of energy will expand rapidly. It is also an opportunity to discover new forms of fuels, power generation and distribution methods.

The concept of solar energy is now well-recognized as an alternative source of energy because, it is abundantly available, it is clean, generates no pollution and it is silent. The major raw materials such as Silica  and Gallium Arsenide  are  also available but some of the rare earth materials used in PV industries and batteries  are available only in certain parts of the world.  China is endowed with many such rare earth resources. For example, Lithium has limited resources and now bulk of it is produced from natural brines similar to the one at Atacama deserts in South America. It is also available in the form of minerals and ores which many countries are now trying to exploit commercially.

The storage of energy from  solar and wind is  done using deep cycle batteries, most of which are Lead-acid batteries. Bulk of the used Lead acid batteries are recycled but the demand for such batteries keeps increasing. As I mentioned in my previous articles, the sheer weight of these batteries, space required to install them, capacity use, capacity constraints, regular need for  maintenance and life cycle are some of the issues that are critical for renewable industries. In deep cycle batteries, discharging stored energy below certain levels dramatically reduces the life span. Hot climate conditions have certain impacts on maintaining such batteries.Life of a battery is critical because when you calculate the cost of energy over the life cycle of 25 years,the several replacements of battaries and their cost will have a dramatic effect on the cost of energy.

Batteries are indispensable tools in energy industries but their usage can be minimized  to a great extent by using Hydrogen as a storage medium. Let us analyze a simple example of a PV solar system for power generation. We made a computer simulation on three  different  scenario for a PV solar system for a small residence with power consumption at 15,500kwhrs/day. First simulation was based on PV solar, direct grid connect, without  storage batteries but connected directly to the grid, assuming the grid power tariff  is at $0.10/kwhrs and sale to grid tariff at $ 0.30/kwhrs.The second simulation was based on grid independent system  using battery  storage for 8 hrs autonomy. The third simulation is also grid independent, but solar power is connected to an Electrolyzer to generate Hydrogen and store it in a tank. We used a small capacity battery, less than twenty percent  of the capacity used in the earlier case and a Hydrogen storage with Fuel cell along with an inverter. The stored Hydrogen was used to generate power to meet the requirement of the residence, instead of supplying power directly from the battery. The cost of energy using direct grid connect was the lowest $$0.33/kwhrs, while Grid independent with battery storage ,the cost of power was $1,20/kwhrs.In third  scenario with Hydrogen and Fuel cell the cost of power was $ 1.90/kwhrs, but there was surplus Hydrogen in the storage tank. With Hydrogen as a storage medium, the cost of power is high due to initial investment but it is maintenance free and ideal for remote locations.

The Hydrogen and Fuel cell solution though expensive, has a several advantages. The power generated by PV solar is stored in the form of Hydrogen instead of storing in batteries. A single battery is used to keep up a steady current to Electrolyzer but bulk of the energy is stored in the form of Hydrogen. Another advantage with this system is that stored Hydrogen can also be used as a fuel for residential heating as well as to fuel your car.

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