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| Fig. 1: Apollo beach power plant. (Source: Wikimedia Commons) |
Fossil fuel plants are the leading electricity producer in the United States. Recent concerns surrounding climate change demand the necessity of moving toward electricity generating options that do not emit carbon dioxide. Nonetheless, Fossil fuel plants such as the Apollo Beach Power Plant pictured on the right (Fig.1) have a massive advantage when electricity demand is low since they can essentially produce just enough electricity to meet the current demand (High Operating Cost). However, when demand for electricity is low, the cost of electricity is increases rapidly for capital- intensive plants operating at part-load (nuclear, wind, solar). For these clean energy options to be more openly adopted, we need to find someway to store or use the excess electricity that is created. [1]
The amount of electricity created into the United States in 2016 was 4,079 million (kilowatt hours) of electricity. The price of this massive market (electricity) is pre-determined everyday (24 hours before) through an auction system between the producers of the electricity and the distributors. [2] The distributers determine how much electricity they will need at the given time and the suppliers will bid in relation to their operating cost for the energy demanded. At the end of the bidding, the grid operator accepts bids up to the demanded amount of electricity. Of the accepted bids, the bid with the highest electricity price sets the price for that hour. Typically, the price that the suppliers are willing to sell at is lower during low-demand times and higher during high-demand times. [1]
This type of system can lead to strange outcomes when clean energy (low-operating cost) can actually meet demand. The price they bid at is so low that the price the grid operator takes will result in such a small or no profit for the plants. This is why there is a need for ways for clean energy to be able to sell their excess energy when demand is low instead of it going to waste and the plants not being profitable.
Storage options for the excess energy created are a large-scale grid of batteries or pumped hydraulic systems. Both of these systems are extremely costly and make renewable energy less profitable than fossil fuels. Forsberg explains how the use of a firebrick storage medium could act as a battery to be used later in high demand situations. [3]
The demand for industrial heat in the U.S is actually larger than the demand for electricity in most industrialized regions. Also, unlike the market for electricity, the demand for industrial heat is constant and could use the additional source of heat (firebricks). [1] Since there is always a demand for heat, when demand for electricity is low, clean energy plants could sell low priced electricity to industries that will always need more heat. [1]
Low-price electricity is used by heating firebricks with electric resistance heaters. The specific bricks that will be heated are very similar to normal bricks, made up of some combination of materials optimized to retaining and insulating head. With insulation, Forsberg predicts that the total heat loss from the bricks will just be 3% everyday. [1] The main use of the firebricks as energy storage would not be reproduction into electricity (although it is possible), but rather to be used for heat.
Essentially, industries would be purchasing low-price electricity at times when demand are low to heat their set of firebricks. Then at times of peak electricity output (high prices), they can use the heat that the firebricks have retained rather than purchase expensive electricity to then turn into heat. They have transformed low-price energy into high-value energy by simply heating up the firebricks when the demand for electricity is low. [1]
© Ben Hallock. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] C. W. Forsberg et al., "Converting Excess Low-Price Electricity into High-Temperature Stored Heat For Industry and High-Value Electricity Production.," Electr. J. 30, 42 (2017).
[2] L. Hirth, "The Optimal Share of Variable Renewables. How the Variability of Wind and Solar Power Affects Their Welfare-Optimal Deployment," Vattenfall GmbH, September 2013.
[3] C. Forsberg, "Development Strategy for Gas Turbines with Firebrick Resistance-Heated Energy Storage to Enable Nuclear-Renewable Grid Integration.," Trans. Am. Nucl. Soc. 116, 857 (2017).
