By MURRAY WALSH
Part three of a four-part series
We have previously examined fossil substances (or maybe we should say carbon-based substances so we can include traditional biomass) and the essential role they play in sustaining the world economy and society. Are there ways to use them to get the energy and heat without harmful emissions?
The answer is yes and two such methods will be discussed here. Hydrogen and oxy-combustion, have “arrived,” so to speak, and they mean that climate activists and fossil fuel defenders can have common cause if they want it.
Hydrogen has been around for centuries as an interesting substance and in various useful roles since the dawn of the industrial age. It is pretty easy to make and there are several ways of doing so. At least one of those ways, electrolysis, splitting the water molecule into pure oxygen and hydrogen, can be done with zero emissions. You do it with electricity.
So, was the electricity generated cleanly? Sure! But we’ll get to that later.
The thing about hydrogen is that it can be used as a transportation fuel like gas or gasoline. It is compressible, even to a liquid state, and thus storable in tanks in vehicles.
The most dramatic recent demonstration of the use of hydrogen was in Elon Musk’s recent sub-orbital tourism rocket launch. Do you remember what the exhaust flare on that rocket looked like? It was a solid blue torch that gave off no smoke or clouds of vapor. It reminded me of the Bunsen burners we used in high school chemistry. The key thing is that when you burn hydrogen, the only emission you get is a cool blue flame and plain old water. To create it, you crack the water molecule with external energy. To use it, you re-combine it with oxygen and blammo! You’ve got power to drive a piston in a reciprocating engine or to provide reaction mass to drive a rocket ship or jet airplane.
Electrolysis is a clean way to generate hydrogen but not very efficient. More efficient ways include cracking carbon-based substances. This is a quote from the USEIA website:
Steam-methane reforming accounts for nearly all commercially produced hydrogen in the United States. Commercial hydrogen producers and petroleum refineries use steam-methane reforming to separate hydrogen atoms from carbon atoms in methane (CH4).
Natural gas is the main methane source for hydrogen production by industrial facilities and petroleum refineries. Landfill gas/biogas, which may be called biomethane, is a source of hydrogen for several fuel cell power plants in the United States. Biofuels and petroleum fuels are also potential methane sources.
On that same federal webpage, other techniques are mentioned as in development or under study:
- Using microbes that use light to make hydrogen
- Converting biomass into gas or liquids and separating the hydrogen
- Using solar energy technologies to split hydrogen from water molecules
The key points here are that hydrogen has great potential as a transportation fuel and that carbon-based feedstocks are increasingly efficient and effective means to obtaining it.
We now turn to the non-transportation side in energy production and that is the facility needed to produce electricity. We have the means to distribute electricity (although it sounds like they need to tune it up a bit in California) but the primary issue is creating electricity without emissions.
Welcome to the world of oxy-combustion. Take a look at the website for NETpower.com/ for a more complete explanation than I can provide here.
Typical power plants, whether fossil fuel-fired or nuclear, use fuel to create heat which is used to create steam that turns a turbine assembly in which there is a rotor spinning within a stator. It is the magic of this spinning motion that produces electricity. In the past, the fossil fuel was combined with air to produce the heat and all manner of emissions spewed forth out the smokestack while the heat was applied to water to make steam.
Oxy-combustion is the mixing of pure oxygen with carbon-based gas to generate superheated high-pressure CO2 that is used instead of water-based steam to turn the turbine. The CO2 – now at low pressure – is then processed, and re-pressurized to be sent back through the system or sent out of the plant in containers for other uses. Not least of these other uses is to inject the CO2 into oil fields to help pressurize the crude oil from beneath to make it easier to pump. This sequesters the CO2.
NETPower has a 50-megawatt plant in Texas that they built to demonstrate the technology. Presumably, they also make money from it. Let’s try to see how much. Fifty megawatts is a lot. It is 50 million watts. Over an hour’s time, that is 50-million-watt hours or 50,000 kilowatt hours.
Electricity is sold by the kilowatt hour. Here in Juneau, we pay about 12 cents for one kWh. The local power company has to pay you the wholesale rate if you contribute power to the system. In Arizona, many homeowners have solar panels on their roofs that result in nearly zero payments to the electric company and maybe even a bit of money coming back because your roof generated more watts than your house needed.
The local wholesale rate here in Juneau was $0.06 per kWh when I looked into it about 10 years ago. So, at that rate, the NETPower plant in Texas is earning about $6,000 per hour. I have no idea how much gas they have to pay for, or how expensive it is to run the plant, but that works out to over $30,000,000 per month! There might be some money to be made in the emission-free energy business.
Also, the NETPower development began with looking at coal as the carbon feedstock but they switched to natural gas for a lot of reasons. This is good for gas and that might be the end of it but there are other forms of gas that are combustible. There is a group of such gases under the general name syngas and one such gas, maybe more, is derived from coal. Others can be derived from petroleum.
The point here is that carbon is the common thread from all these feed stocks and all of them, including traditional biomass and landfill emissions could eventually feed an oxy-combustion plant.
This all sounds like the new energy holy grail, right? Well, yes it does and I am sure you will be hearing more about it in the years to come, but just remember where you heard about it first, okay?
Next in the series, how to use these new-fangled things in the near future.
Murray Walsh is part of the extended MRAK writing staff in Juneau. Check back for Part 4.