Jan 20, 2023Liked by Peter Ehrlich

I like this post overall, especially the part about austerity. You briefly mentioned carbon generated by electricity generation, but I think this needs to be looked at in more detail. I looked into it a bit earlier in 2022 and decided to buy a hybrid since it actually seemed to be a better choice than a BEV in terms of overall carbon emissions based on the electricity generation mix in most of the country. If you have mostly renewable sources to charge from then it is a different story, but currently I think this only exists in some pockets of the country. Or if you have your own solar generation. One problem with solar, there is an issue with seasonal supply and demand. Much more energy is generated in the summer than in the winter, but sometimes demand in the winter is higher, especially if people are using heat pumps in cold regions. I'm looking into doing a combined solar plus CHP system at home. The CHP system provides heat and electricity in the winter and the solar system would provide electricity mostly in the summer. I'll still be burning #2 fuel oil (transitioning to biodiesel) but the overall efficiency is much higher than generating electricity at a natural gas/oil fired power plant, so overall carbon emissions can be reduced. I think we really need to look at practical ways to reduce carbon emissions quickly, not necessarily completely eliminate it since that will take a lot more time. If everyone drove a hybrid vehicle for example, I think we would see a very significant reduction in emissions and it is very practical since it does not cost that more than a traditional ICE vehicle and uses existing infrastructure. Infrastructure build out takes a lot of time and I fear that if we jump to EVs before there is enough renewable generation it will not actually reduce carbon emissions enough. Along with renewable generation I we will need some form of long term energy storage to resolve seasonal fluctuations in renewable generation and demand. This could end up being hydrogen, but we are not there yet. For now, I think we will still need to burn some fuel to stay warm in the winter. if it is done efficiently we can still reduce emissions. I know someone you built a very elaborate solar heating system, but in the coldest months of the year in VT it is not enough, so he still burns wood in a boiler for additional heat. Burning biomass on a small enough scale can be sustainable for now I think, until we come up with better solutions.

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Great to hear from you Leif! Long reply here, you've sparked some ideas I've been mulling over. Will be curious to hear how your plans progress.

I hadn't heard of CHP before this - very interesting. This video seemed like a good introduction to the idea: https://www.youtube.com/watch?v=vcaGQDstDug . It's terrific that the efficiency beats a Natural Gas plant, which unfortunately is our "price to beat" today. I'd love to see the napkin math on that if you have it around.

Along similar lines I've often wondered how the lines cross for thermodynamic efficiency of large central engine generations generating power (versus ICE), in comparison with the electric losses during transmission. Of course this is very dependent on exactly how the lines are set up.

I'm trying to think about how CHP fit into a net-zero 2050 strategy, and having a little bit of trouble with it. One would hope a system would last fifteen years at least, and furnaces etc can sometimes twice that with a little luck. Fifteen years from now is 2038, and the Paris Agreement calls for a 45% reduction by 2030 and reach net zero by 2050. So this would work if every sector of every country reaches 45% reduction seven years from now, but I'm afraid realistically the progress will be far from uniform. E.g., developing countries are saying "hey, we're poor and dealing with a lot, we should have a 2060 timeline, and The West should have a 2040 timeline".

Although - I haven't done the math here on how a BioDeisel reduction reduces GHG, maybe that's a way? If we can solve for net-zero nitrogen fixation, ammonia powered tractors, and so on...

You're right about the difficulties of our current electrical grid though - it's not great (electricitymaps.com is a great interactive tool here), and our investment is too slow. AFAIK the only way to speed this up is with pressure from ordinary citizens demanding change, and a big way to get that is for people to fully commit in the ways which they can (e.g. getting the consumption infra in-place ahead of the generation side), becoming in to true stakeholders in low-GHG future.

Another area I'm curious about - could we build solar so that we can be solar powered almost completely in winter (do bi-axial mounts reduce the seasonality by a significant amount?), and in the summer find other uses for the surplus power. Such as pumping water back in to Canadian reservoirs, running industrial processes such as DAC or Nitrogen fixation, or sending the power south.

I would love to work on some of the problems you mention. Big issues are solar permitting reform in Vermont, energy storage, and IMO almost all states are behind on Net Metering for Energy Storage @home, which will be a big role for EVs in the future. (Not possible now, as an EV used for storage will degrade its battery, which owners must be compensated for).

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Hi Peter,

The napkin math for CHP is as follows: I normally use about 715 gallons of oil annually and 5400kWh of electricity. In NH the current data I can find for GHG emissions per kWh is 0.289lbs. That is much better than the national average of 0.818lbs, but I think it could have gotten a bit worse recently due to higher natural gas usage compared to nuclear. Oil emits 22.38lbs of CO2 per gallon burned, so in total my CO2 emission currently is 17,562lbs annually. If I run a CHP system to meet by heating load I would burn 952 gallons and would generate a surplus of 6,206kWh. If I burn straight oil I would generate 21,283lbs of CO2 and offset 1,800lbs that would normally be emitted to generate the electricity. The net is 19,500lbs, so this is actually worse. However, if I burn B20 the net will be 15,913lbs which is a 10% reduction. This is assuming that B100 has 74% lower CO2 emissions compared to petroleum diesel. As you increase the percentage of biodiesel it gets much better. With B50 there will be a 40% reduction, B100 90% reduction. Also I would save about $2,000 per year in energy cost. This could also be done with propane as a fuel, but propane is about on par with B20 in terms of CO2 emissions. Biogas is another option.

Electricity transmission losses are about 10% I think, so not that bad. Even so CHP when used correctly can beat the overall efficiency of any thermal plant since all of the heat is being used. It only works in certain applications though. You need a big enough heat load. Here in New England we have a big heat load in the winter, so plenty of electricity would be generated in the winter. In the summer this would taper off a lot, the only heat demand is domestic hot water. But this is where solar generation comes it. It is possible to size solar generation to cover the demand in winter and then curtail it in the summer, but this becomes a big investment that does not pay back quickly. If the energy can be stored all summer long and used in the winter that would be a solution. There are many possible technical solutions to that; biofuels being one of them. Also hydrogen storage, or other forms of heat storage. For now I think biofuels makes sense for me in the short term because it can be done with existing technology that I am familiar with. I can buy biodiesel and store it in my existing tank. Generating and storing hydrogen is a whole different story. I'm sure there are other things I haven't thought of though.

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This is really great! I love the level of detail. It is inspiring - would be fun to make a model in a little web widget which can be tuned to different regions and economic models, so that others can play with it..

I have heard good things about ground-mass heat pumps which just store the extra summer heat underground. Not sure if those work generally or are best in particular soil conditions though.

Edit: Found this chart on a report of fuel carbon intensities from VT Energy Action Network's 2022 report: https://imgur.com/a/qItq30R

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That chart is interesting, I hadn't heard about renewable propane before. When it comes to biofuels I think we do have to be careful how much we use. It is renewable only to a certain point. It is best to use waste streams as the feedstock and existing cultivated land. Otherwise it is kind of like cutting down a forest to install ground mount solar panels. Also, solar panels can produce a lot more energy per acre than biofuels, maybe even 100 times more on an annual basis depending on location. But often biofuels are a side product of other agricultural products and waste streams, so a lot of things to consider. For now, I think limited use of biofuels can make sense, especially where natural gas pipelines are not available, because otherwise people are generally burning regular fuel oil which emits twice as much CO2 compared to natural gas.

I have looked into ground source heat pumps. When it comes to ground source heat pumps the problem for me was the initial investment was very high and electric rates are $0.31 per kWh so the operating cost is not really that low. It probably would reduce GHG emissions a bit though since the generation here is relatively clean, not many coal burning plants left in New England.

I haven't heard of ground-mass heat pumps but if that is practical it could make sense.

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Jan 18, 2023Liked by Peter Ehrlich

My favorite part was hearing about your experience with an electric car!

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