Skip navigation

Category Archives: Hydrogen storage

 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.

 

It is clear substituting fossil fuels with Hydrogen is not only efficient but also sustainable in the long run. While efforts are on to produce Hydrogen at a cost in par with Gasoline or less using various methods, sustainability is equally important. We have necessary technology to convert piped natural gas to Hydrogen to generate electricity on site to power our homes and fuel our cars using Fuelcell.But this will not be a sustainable solution because we can no longer depend on piped natural gas because its availability is limited; and it is also a potent greenhouse gas. The biogas or land fill gas has the same composition as that of a natural gas except the Methane content is lower than piped natural gas. The natural gas is produced by Nature and comes out along with number of impurities such as Carbon dioxide, moisture and Hydrogen sulfide etc.The impure natural gas is cleaned and purified to increase the Methane content up to 90%, before it is compressed and supplied to the customers. The gas is further purified so that it can be liquefied into LNF (liquefied natural gas) to be transported to long distances or exported to overseas.

When the natural gas is liquefied, the volume of gas is reduced about 600 times to its original volume, so that the energy density is increased substantially, to cut the cost of transportation. The LNG can be readily vaporized and used at any remote location, where there is no natural gas pipelines are in existence or in operation. Similarly Hydrogen too can be liquefied into liquid Hydrogen. Our current focus is to cut the cost of Hydrogen to the level of Gasoline or even less. Biogas and bio-organic materials are potential sources of Hydrogen and also they are sustianable.Our current production of wastes from industries business and domestic have increased substantially creating sustainability isues.These wastes are also major sources of greenhouse gases and also sources of many airborne diseses.They also cause depletion of valuable resources without a credible recycling mechanisms. For example, number of valuable materials including Gold, silver, platinum, Lead, Cadmium, Mercury and Lithium are thrown into municipal solid waste (MSW) and sewage. Major domestic wastes include food, paper, plastics and wood materials. Industrial wastes include many toxic chemicals including Mercury, Arsenic, tanning chemicals, photographic chemicals, toxic solvents and gases. The domestic and industrial effluents contain valuable materials such as potassium, Phosphorous and Nitrates. We get these valuable resources from Nature, convert them into useful products and then throw them away as a waste. These valuable materials remain as elements without any change irrespective of type of usages.Recyling waste materials and treatment of waste water and effluent is a very big business. Waste to wealth is a hot topic.

The waste materials both organic and inorganic are too valuable to be wasted for two simple reasons. First of all it pollutes our land, water and air; secondly we need fresh resources and these resources are limited while our needs are expanding exponentially. It is not an option but an absolute necessity to recycle them to support sustainability. For example, most of the countries do not have Phosphorous, a vital ingredient for plant growth and food production. Bulk of the Phosphorus and Nitrates are not recovered from municipal waste water and sewage plants. We simply discharge them into sea at far away distance while the public is in dark and EPA shows a blind eye to such activities. Toxic Methane gases are leaking from many land fill sites and some of these sites were even sold to gullible customers as potential housing sites. Many new residents in these locations find later that their houses have been built on abandoned landfill sites. They knew only when the tap water becomes highly inflammable when lighting with a match stick. The levels of Methane were above the threshold limit and these houses were not fit for living. We have to treat wastes because we can recover valuable nutrients and also generate energy without using fresh fossil fuels. It is a win situation for everybody involved in the business of ‘waste to wealth’.

These wastes have a potential to guarantee cheap and sustainable Hydrogen for the future. Biogas is a known technology that is generated from various municipal solid wastes and effluents. But current methods of biogas generation are not efficient and further cleaning and purifications are necessary. The low-grade methane 40-55% is not suitable for many industrial applications except for domestic heating. The biogas generated by anaerobic digestion has to be scrubbed free of Carbon dioxide and Hydrogen sulfide to get more than 90% Methane gas so that it can be used for power generation and even for steam reforming to Hydrogen generation. Fuel cell used for on site power generation and Fuel cell cars need high purity Hydrogen. Such Hydrogen is not possible without cleaning and purifying ‘ biogas’ much. Hydrogen generation from Biogas or from Bioethanol is a potential source of Hydrogen in the future.

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.

%d bloggers like this: