Wednesday, February 16, 2011

Hydrogen Production as a Load Balancing Option

Despite my personal bias toward hydrogen fuel cell vehicles, hydrogen production has made a lot of sense to me even if it is not the transportation fuel of the future I think it is. As a matter of fact, the options hydrogen provide is the main reason I think is our future fuel.

Co-generation is a great way to improve efficiency of any kind of power plant. To get the maximum benefit of co-generation and some other power options, hydrogen is interesting.

Combination power and heat is a basic co-generation design. Waste heat, normally in the form of hot water or steam is used to heat something that needs heating. Northern Europe and to a lesser extent the US has hot water piping used to provide hot water for building heating and industrial applications. Most industrial applications are designed so that there is a pretty equal demand for both the power and the heat so the plant can operate at peak efficiency. Hot water demand varies widely in building heating applications which means some other use of the hot water is needed or the efficiency is greatly reduced. There are a lot of ways that the excess heat can be used, but often it is just sent to the cooling towers and is lost.

Sulphur-Iodine cycle thermolysis is an efficient process to produce hydrogen developed by General Atomics in the 1970's. It was developed as a co-generation process for nuclear power plants, but can be used with any heat process, fossil fuel, solar or geothermal for examples. Hydrogen itself is not an energy source it is just a storage state for energy, like a gas battery if you will. Hydrogen production using S-I cycle can be used in state of the art tri-cycle co-generation. An example would be electric from a super critical steam turbine with the high temperature steam out of the turbine powering the S-I cycle and the lower temperature condensate (hot water) being used for a heating purpose or pumped back into the boiler to save energy. The Hydrogen produced could be used to power a peak demand gas turbine for power or used for transportation fuel or enriching natural gas. So fuel cells do not have to make a big splash in transportation for the hydrogen to be useful.

A tri-cycle co-generation plant can operate at nearly 90% efficiency which is crazy efficient! A typical coal plant without co-gen is about 40% efficient and a normal co-gen plant could hit about 80% efficient, but 60% is more common. Hydrogen production does knock the efficiency of tri-cycle down in some cases to around 75%, but that is still pretty good use of fuel. The hydrogen part of the tri-cycle is not required, but it has advantages in a number of cases without transportation fuel needed as a product.

As I wrote before, there is a lot of money invested in coal power plants in the US. Some coal plants are being converted to natural gas, but natural gas infrastructure limits how many can be converted. Retrofitting a good number of coal plants to dual cycle and tri-cycle co-generation just makes too much sense economically not to happen.

Converting to natural gas reduces carbon dioxide emissions by half of what was produced by the coal, but doubling the efficiency of coal does the same thing. That means co-generation in natural gas powered plants is probably going to happen to maximize efficiency and minimize CO2 emissions. Another opportunity for hydrogen production.

Wind and solar power is intermittent which makes integration with the national grid a little more challenging. Electrolysis production of hydrogen is less efficient that S-I cycle, but using electricity at 40% efficiency in hydrogen production is better than wasting it entirely. So there are applications there depending on options in the area the power is produced.

Coal gasification, one of the "clean coal" options, decomposes coal into its basic elements carbon and hydrogen plus a few other elements. Then a variety of products can be made from the basic building blocks or the hydrogen burned to create energy. The creativity of chemical engineering minds will determined how well those building blocks are used. Anyway, another potential source of excess hydrogen.

The S-I process was developed for generation IV nuclear power plants, so there is yet another potential source of excess hydrogen.

Just looking at all this, I just cannot see a hydrogen energy economy not being in our future, but then I am not in charge. I have mentioned all of this before, but I put it together this way to look at the economic aspects of future energy production. I hate statistics, but they can be useful in the proper hands. So looking at existing investment in different areas of energy production and use, a more accurate estimate of which technologies, in which proportions and how much it is all going to cost may be made. I want to look at it in a US only perspective. While UN mandates sound like the plan for some, the UN's track record is not that impressive to me. It is more likely that one of the group of six, or the group of six, will start plotting their own course in the hopes that the rest of the world will follow.

So I will review this and once it is cleaned up try to start a discussion with people more experienced in the different areas.

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