There are many instances where microwaved food comes in handy. While standing and waiting for the food to be heated, have you thought of what goes behind generating electricity? Different energy sources generate power. Electricity companies go through many obstacles to provide power in every instant of time. After the energy is produced, the grid balances supply and demand of electricity from all sources. Over the past decade, the production of renewable energy sources has increased, this is where the problem is created. For example, solar plants can only produce energy when there is sunshine and wind turbines depend on the airflow which sometimes is not consistent. As the renewable energy source becomes less stable, the companies back up with non-renewable sources (e.g., natural gas) to adjust inherent change. An alternate form of a constant and carbon-free source is nuclear energy. Nuclear power splits atoms in the reactor to heat water producing steam. The steam is used to spin turbines to generate electricity.
Nuclear plants are operated at full power 24/7 to meet the customer’s demand, leaving the plant to overproduce or underproduce depending on the market. To solve this problem, nuclear plants have considered a load-following technique. Load following is best defined as a change in the power output of the reactor to meet the current grid demand. Our senior design group at North Carolina State University has analyzed more on this procedure. In partnership with GE-Hitachi, their reactor model that is currently being developed is used for this load following analysis. To analyze the reactor, the system’s code has been designed to calculate the system response of its output. Also, an external system has been considered as an option to bear the load-following responsibility and allow the reactor to operate at base load (full power).
To begin, we created a code that the thermal hydraulics of GE-Hitachi’s reactor. This code helps to analyze the system’s behavior when it outputs energy according to the grid demand. It also consists of rector physics that helps to analyze the load following capabilities in the reactor more accurately.
Another solution is an external energy storage system that will help to load follow instead of the reactor. This system will have an electrical and a mechanical option that can be coupled to the reactor. For the electrical option, there are fuel cells and electrolyzers. Full cells are devices that produce electric current from chemical reactions. Hydrogen electrolyzers are devices that use electric current to split water molecules into hydrogen and oxygen gases. A stack of fuel cells can provide extra power when the reactor under-supplies the grid demand. Likewise, hydrogen electrolyzers will produce pure hydrogen gas when the reactor overproduces. The hydrogen gas can be stored or used for other purposes. For the mechanical option, the excess energy can be stored by using a Thermal Energy Storage (TES) system. This system captures the heat of the unused steam and stores it in an appropriate medium. The stored energy can later be used for power generation or heating and industrial applications.
As a result, the system code successfully runs and calculates the parameters of the reactor. The code also analyzes different phase dependencies put on the reactor during load following. The external energy storage system will help the reactor by not adding the additional wear and stress caused by the load following.
The levelized cost of electricity (LCOE) is used to determine the economic viability for load following. The LCOE gives the price at which electricity must be sold to break even with the cost of the system. The load following operation adds more thermal and mechanical stress on the reactor, which increases 2% of operation and maintenance costs. Whereas, the energy storage system does add an additional charge because of fuel cells and electrolyzer, it is the most expensive option. In the future, the demand for fuel cells and electrolyzers could potentially increase, and thus, the cost of this electrical system will reduce.
Instead of improving the way to make renewable sources better, more time can be invested in nuclear power. Nuclear energy provides a clean, carbon-free, scalable, and constant power supplying system. It is also more reliable than any other renewable sources. These options may not be economical now but can be considered in the future as the cost will reduce.
Netra Patel is a transient student studying nuclear engineering.
