So, i’ve been thinking — a large percentage of my energy consumption is from air conditioning, energy demands on the grid vary through the day, and the temperature usually is cooler at night, when the sun isn’t out.
So, why can’t we build big “coldness reservoirs” underneath our homes. The idea is this: get an extremely insulated system. When energy rates are cheapest, make the system cool off the fluid inside the system. Later, when energy rates are higher, use the fluid productively. You could use it as part of your air conditioning system, you could use the heat difference as part of a reverse-peltier effect to generate some electricity, etc.
Of course, you could change the actions depending on what the situation is (heat vs. cold and when the rates are high) — you could imagine some future scenario where rates are higher at night because there’s no sunlight (and thus we’d have to rely on gas, coal, etc)
Anyway, why doesnt this work? I could imagine that you’d need to store way more energy than would be possible to do economically. Water’s got a pretty high specific heat — if you could use water, you’d probably need to store so much water that you’d end up having to have a couple swimming pools full of water stored underneath your home, and that can’t be cheap. Also, to be effective, you’d probably need to supercool/superheat the water to the point where you’d be losing energy through system inefficiencies.
Anyway, it’s an idea.
Demand and supply are the major components of the cost of electricity. If we lower peak demand, supply will increase and the cost of power will fall significantly.
The primary method available to reduce demand is to make ice when electricity is cheap. Melt the ice for air conditioning when electricity is expensive or in high demand. This is a simple alternative to spending billions building new coal fired electric power plants.
Thermal Energy Storage, TES systems have been in use in Texas since the 1920’s in Dallas when three churches installed systems. One of the original applications was to use a small inexpensive compressor to make ice all week long and then melt all that ice to cool the sanctuary for two hours on Sunday. A common TES system is using tank type water heaters (hot thermal storage) to avoid large instantaneous gas or electric water heaters.
So why don’t we find a TES air conditioner in every house and small business? The answer is also simple:
• Most electric rates are averaged so it is not less expensive to buy electricity when it should be cheap and it is not more expensive to buy electricity in high demand periods when the price should be exponentially higher.
• In very round numbers it costs thousands of dollars per kW (or ton of A/C) to fund the construction of electric generation plants, transmission and distribution (TD) infrastructure. There are no mechanisms to divert funds from coal fired generators to funding TES systems in your home or business. The current conservative estimate of avoided costs to build generation, transmission and distribution infrastructure is $1000. per kW per year. This adds up to more than $45,000. over the 15 year life of a 3 ton TES system.
Should we invest $45,000 in new coal generating plants or invest a fraction of that in your home TES system?
If the above economic rationalization isn’t enough to convince you, consider the following additional benefits on TES.
• Running your air conditioner at night to make ice for daytime use is much more efficient because the ambient outside temperature is much lower and you’re a/c unit operates more efficiently.
• Running the generating turbine at night is much more efficient for the same reason, lower nighttime temperatures.
• All power plants run more efficiently when they are fully loaded and demand is predictable.
• Transmission and distribution is more efficient at night.
A massive deployment of TES will postpone the need to build additional power plants for many years and lower the cost of power for consumers. We can land on the moon. Why can’t we make ice?
There have been various methods of storing specific temperature in a thermal mass for later use over the years. One of my fav was people who turned their basement into a giant rock pile to store heat. Nothing better than trying to control insects in a quarry…..
But ya, geothermal is a great source of heating and cooling and is nice and steady temp year round. I’d vote for that first because we don’t have to worry about the structure of the house, etc.