Session: 02-08: Balance of Plant

Paper Number: 64638

Start Time: August 6, 2021, 03:15 PM

64638 - Nuclear Air-Brayton Combined Cycles Using Electrically-Heated Conductive Firebrick Heat Storage and Hydrogen for Peak Power 

A low-carbon world needs a replacement for the combined-cycle gas turbine to provide variable heat and electricity. The goal of a low-carbon electricity grid and the large-scale addition of wind and solar have resulted in highly-volatile wholesale electricity prices including times of near-zero wholesale electricity prices. The high capital costs of nuclear power plants create economic incentives to operate these plants at base-load. We describe herein a Nuclear Air-Brayton Combined Cycle (NACC) with an electrically-heated thermal energy storage (E-TES) system where the reactor operates at base-load with variable electricity to the grid to maximize revenue.

 

Most of the time the NACC operates at base-load. NACC is a multi-reheat gas turbine combined cycle plant with nuclear heat used to heat compressed air up to 700°C. The heat can come from any high-temperature reactor or high-temperature Concentrated Solar Power (CSP) system. At times of low electricity prices, electricity from NACC and the grid is converted into high-temperature stored heat in the form of hot firebrick. At times of high electricity prices compressed air is first heated to 700°C using nuclear heat and then is further heated by sending the air through hot firebrick to heat the air up to 1427°C before going through the turbine and then to the heat recovery steam generator. The hot firebrick is the high-temperature heat source for a NACC thermodynamic topping cycle—raising turbine inlet temperatures from 700 to 1427°C. The round-trip electricity-to-heat-storage-to-electricity efficiency is above 70%; that is, if one unit of electricity is sent to heat storage, more than 0.7 units of peak electricity are returned. The temperature limits of the heat exchangers between the nuclear reactor and NACC determines the maximum temperature of nuclear heat input while the temperature limits of actively-cooled turbine blades determines peak temperatures associated with the thermodynamic topping cycle. The allowable peak temperatures of the firebrick are far above allowable peak temperatures of the gas turbine blades.

 

Previous work has examined NACC with thermodynamic topping cycles burning natural gas, biofuels and hydrogen. What is new is electrically-heated conductive firebrick that enables electrically heating firebrick to very high temperatures with high roundtrip storage efficiencies. The design and integration of E-TES system are described. The power cycle enables base-load nuclear plants to be a replacement of conventional natural-gas-fired gas turbines for providing variable electricity and heat.

Presenting Author: Charles Forsberg Massachusetts Institute of Technology

Authors:

Charles Forsberg Massachusetts Institute of Technology
Daniel Stack Massachusetts Institute of Technology
Patrick Mcdaniel University of New Mexico