For example, bricks to be placed in the center of the assemblage could have high thermal conductivity, so that they can easily take in heat from the resistance heaters.These bricks could easily give up that heat to cold air being blown through the mass to carry away the heat for industrial use.At a later time, the heat could be used directly for industrial processes, or it could feed generators that convert it back to electricity when the power is needed.
Firebrick itself is just a variant of ordinary bricks, made from clays that are capable of withstanding much higher temperatures, ranging up to 1,600 degrees Celsius or more.
Virtually dirt cheap to produce — clay is, after all, just a particular kind of dirt — such high-temperature bricks have been found in archeological sites dating back to around 3,500 years ago, such as in iron-smelting kilns built by the Hittites in what is now Turkey.
“In electricity markets such as Iowa, California, and Germany, the price of electricity drops to near zero at times of high wind or solar output,” Forsberg says.
Once the amount of generating capacity provided by solar power reaches about 15 percent of the total generating mix, or when wind power reaches 30 percent of the total, building such installations can become unprofitable unless there is a sufficient storage capacity to absorb the excess for later use.
The fact that these bricks have survived until now testifies to their durability.
Nowadays, by varying the chemical composition of the clay, firebrick can be made with a variety of properties.
At the end of each auction, the distributors figure out how many of the bids will be needed to meet the projected demand, and the price to be paid to all of the suppliers is then determined by the highest-priced bid of all those accepted for that hour.
But that system can lead to odd outcomes when power that is very cheap to produce — solar, wind and nuclear power, whose actual operating costs are vanishingly small — can supply enough to meet the demand.
Distributors determine how much power they expect to need during each hour, and suppliers bid based on their expected costs for producing that power.
Depending on the needs at a given time, these prices can be low, if only baseload natural gas plants are needed, for example, or they can be much higher if the demand requires use of much more expensive “peaking” power plants.
At present, the options for storing excess electricity are essentially limited to batteries or pumped hydroelectric systems.