You may not have heard of exergy. (No, it’s not a typo!) In thermodynamics, exergy is the maximum useful work possible as a system resolves into equilibrium. Okay, that’s not a law so much as an inherent property. But the Second Law of Thermodynamics (a true law!) means we are fools not to pay attention to exergy.
|Standard physics torture|
Don’t worry; I’m not going to torture you with equations. The Second Law just says that energy available to do work in a system always decreases over time. Once this energy is gone, you don’t get it back. Let’s examine why exergy is important and what to do about it.
We burn fossil fuels to do work for us, fuels such as natural gas and gasoline. Both are nifty, high quality fuels that contain excellent amounts of exergy. The problem is we use these fuels incredibly inefficiently, getting out of them only a fraction of their potential. And once we burn and waste them, they’re gone. The work they could’ve done for the human race, if only we didn’t squander them, is dissipated forever.
For instance, natural gas can be used to create very high heat. Greater than 800 °F heat. The kind of heat necessary for industrial processes, like glass and cement manufacturing. The kind of heat difficult to get from solar concentrators or solar boilers. Using natural gas to heat air to 72 °F or hot water to 120 °F is a gross waste of natural gas exergy since such low grade heat can easily be generated by a solar hot water heater or a heat pump. Or . . . wait for it . . . the heat can be scooped up from waste heat left over from industrial processes. Indeed, waste heat from industrial processes in the US could heat every single home and business if we set up systems to take advantage of it. (Instead, we squander.)
|Busy making gas?|
Now, natural gas is not infinite. The earth can potentially continue to make small amounts, but it takes millions of years. Methane can also be captured from livestock, sewage and landfills, but in relatively small amounts. In fact, natural gas is so finite, we’re spending more and more energy drilling and fracking to obtain it, reducing the net energy we get from it. Yes, natural gas is cheap at the moment due to US drillers borrowing endless cheap money courtesy of the Federal Reserve even though they’ve been unprofitable for years. Easy credit for drillers has come to a halt, however, and much of the natural gas industry is heading towards bankruptcy. Long term, our grandchildren and great-grandchildren may actually appreciate some natural gas left for them to allow them to produce aluminum, iron and steel, not to mention cast metal. (Electric arc furnaces luckily can be used for making steel from scrap feedstock.)
|Leaks in Boston alone|
The other problem with our current natural gas system is that it involves incredible amounts of pipe to deliver it to where businesses and households can burn it. About two million miles of pipe. Now, natural gas is primarily made up of methane, which, when it leaks into the atmosphere, is twenty times more potent than CO2. And leak it does. Over ten percent of US methane emissions occur from leaks in the natural gas transmission, storage and distribution system. Even though natural gas burns cleaner than other fossil fuels, the amount that leaks does almost as much climate damage as nastier fuels.
Natural gas also poses dangers to homes and businesses via explosions (such as the San Bruno pipeline explosion in 2010 that killed eight people), and through carbon monoxide poisoning, (usually the result of poorly ventilated appliance or heating systems.) Homes and communities that are all electric have fewer potential safety hazards.
What? I’m proposing giving up natural gas for home heating and appliances? Is this even possible? Yes, dear reader, it is. It can be done expensively (all in one fell swoop,) or it can be done economically, by replacing systems and appliances one at a time as they get creaky and old.
The one fell swoop method. If you have gobs of money hanging out in a mutual fund, this is the route I would take. In six weeks you could not only transition to all electric, you could transition to net zero energy and pretty much zero energy bills for the rest of your life. You would have energy security and a low-carbon conscience to boot.
First, install a ground-sourced heat pump, a super-efficient, quiet, and long-lasting way to heat and cool your home ($30K, $20K after tax credit.) Add on a desuperheater that will give you free hot water during summer cooling season ($500), and a heat pump hot water system or solar hot water system to provide hot water the rest of the year ($2K for heat pump version; $5K for solar, $3.5K after tax credit). Then put in an induction/convection stove ($1400-$6000 depending on how high-end). Many professional chefs say that induction ranges cook better than gas ones. Next, get a heat pump dryer ($1400). (If you don’t already have a front load washer, get one of those, too.) After that’s in, slap up a couple dozen solar panels on your roof (probably $15K after federal tax credit), and if your house is reasonably well sealed and insulated you’ll be in great shape. If your local utility is hostile to paying you for the extra electricity your solar panels produce during the day, then install a Powerwall battery for $7K ($5K after tax credit when installed with solar PV) that will allow you to hardly pull from the grid at all.
Total cost to go zero carbon, zero net energy, nearly zero electric bill (with extremely nice, high-end appliances)–$47K. ($52K with Powerwall.) The average US household in 2015 pays about $3200 per year in energy bills (electricity plus fossil fuels burned.) Energy costs are projected to increase 1% per year over time. (I think this is far too low, but hey, we’ll go with it.) So by going all electric/solar PV your energy savings will totally pay for everything in 14 years. (16 years with a battery.) After that your utilities are basically free in perpetuity. Again, this is all averages. Depending on your climate, and the solar insolation of your particular house, your optimal set up may differ.
Note: if you are building a home from scratch, put in radiant-heated, hydronic floors and a drain heat recovery system to produce even higher savings. Harder to do as a retrofit.
The bit-by-bit method. Not all us of have $50K hanging around, so this approach is likely the most viable.
All heating, cooling and appliance systems get old and fail. The trick to replacing them with electric is to not wait until they are totally dead. If your hot water heater goes out at 8pm and you call an emergency repair guy to come over stat with a new unit because you can’t face a morning without a hot shower, you are not going to end up with a heat pump or solar hot water heater. Both take a little more planning.
Let’s look at some life expectancies.
Gas dryer—13 years
Gas stove—14 years
Gas or electric water heater—10 years
Furnace 15 – 25 years
|This may not tell you much, but I can’t resist the animation.|
Because these systems and appliances last so long, it’s vital not to lock yourself into another decade of natural gas use. Look at it this way: there are many ways to generate electricity, many ways that are even low carbon and renewable. Moreover, over the next decade, most households and communities in the US will produce at least some of their own electricity. Few will produce much natural gas. When you have to buy a new heating system or appliance anyway, upgrading to a high-efficiency electric one costs little extra, especially when compared to future energy savings. And you don’t have to put in an expensive ground-sourced heat pump to go all electric. While somewhat noisier and less efficient, air-sourced heat pumps that both heat and cool are far cheaper (only $3K-$5K), and there are new ones out that can deal with temperatures below zero degrees (even -15°F), though if you often have temperatures this low, some kind of back up is recommended. You can even go with a standard electric dryer and electric stove that are almost identical in cost to their natural gas versions, although I encourage you to seriously consider induction cooking.
|Get thee gone|
The exceptions to the bit-by-bit replacement rule are houses heated with oil, propane, kerosene, and/or baseboard electric heaters. These fuels are so costly, and baseboard heaters are so inefficient, that you’re better off replacing them with a ductless heat pump right away, even if the heating system you have is nearly brand new. (Note: if you heat your house with wood, you should already have a masonry heater, a high efficiency woodstove or a high efficiency fireplace insert. Anything else pollutes, squanders resources and significantly wastes your money.)
Also consider lower-tech solutions, like clotheslines for drying, passive solar and/or adding thermal mass for heating and cooling. And then there are ceiling fans, whole house fans, awnings, and southerly deciduous trees for cooling, not to mention sealing and insulating your home to reduce your heating and cooling needs in the first place.
|SESI (the future)|
During my investigation of the all-electric trend, I had a chance to tour the Stanford Energy System Innovations (SESI), a new energy plant that the university is deservedly proud of. Stanford has a district heating system, meaning that the majority of campus buildings (over 150) are connected to a central energy system that provides them with heating and cooling. Stanford used to have a cogeneration energy system that burned natural gas to produce both heat and electricity. Cogeneration was all the rage thirty years ago when Stanford put it in, and it’s indisputably more efficient than power plants that burn natural gas for electricity and then do nothing with the waste heat. (Like 90% of US power plants. Squander, squander.) And cogeneration is also more efficient than burning natural gas for low grade heat and producing no electricity whatsoever, like the average home’s furnace. (Squander, squander.)
|Waste not, want not|
But Stanford’s cogeneration system was nearing the end of its lifecycle, so the university assessed its options. It was then that their team of engineers realized that Stanford’s heating and cooling loads overlapped to the point that they could take the waste heat from cooling and use it to meet 70% of the university’s heating needs. Their team also realized that their current heat delivery mechanism—steam—was far less efficient an energy carrier than hot water and much less safe. So the university replaced 20 miles of steam pipes with 20 miles of insulated hot water pipes, while at the same time building a new energy facility with massive electric heat recovery chillers and three monolithic thermal storage tanks.
SESI went on line this last spring. It has cut Stanford’s carbon emissions in half and will save Stanford $420 million over the lifecycle of the system. It’s also dropped Stanford’s potable water consumption by 15%, water that used to go cooling towers to evaporate waste heat. (Squander, squander.)
|Down is good|
When I toured SESI, I learned that Stanford isn’t completely off natural gas. They still use some during cool weather to boost hot water temperatures in their thermal storage tanks, and they use some in a scattering of older campus buildings that aren’t part of SESI. But with SESI, Stanford is very likely the largest district heat and cooling system in the world to go (nearly) all electric. Stanford is also installing 5.5 MW of solar PV on campus and 73 MW off site to provide the campus with renewable energy. By 2017, their total greenhouse gas emissions will be 68% less than their 2013 emissions.
I have to say, I am such an energy geek, I thought SESI was pretty fabulous and have extolled its virtues to my family well beyond their patience. My college-student daughter, who had to study SESI for a class, thinks I’m nuts.
|You don’t actually need hard hats in a groovy control room|
But after even more research, my enthusiasm has not diminished. Stanford looked into the future, saw where technology and humanity were headed, and converted from 100% fossil fuels to nearly 100% electric, sensibly making good use of waste heat in the process. Yes, Stanford has buckets of money to play with, but as they point out, though SESI combined with renewables had the highest up front capital costs, it was the lowest cost option when taking into account the entire life of the project. (And their calculations didn’t include the possibility of a carbon tax.) In addition, SESI has reduced Stanford’s water consumption no small amount, especially important given California’s drought.
As a country, we will all be off natural gas by 2030 except for high heat industrial processes. There’s no way the planet can stay below a 1.5°C warming increase if we don’t. The cheapest way to do this is to go electric as each appliance and heating system needs to be replaced. Starting now. Basically, there needs to be no more new gas-burning appliances sold or installed in the United States. Starting tomorrow.
Let’s be smart and pay attention to exergy. Let’s only burn natural gas for its high level uses, which certainly don’t include space and water heating. Future generations will thank us.