We focus on implementing innovative technologies that reduce both costs and environmental impact of producing electricity.
The Food-Energy-Water Nexus describes the inextricable relationship between food security, energy security, and water security. A change in any one of these areas affects the entire dynamic, and the stability of each area is vital to a high quality of life. What we advocate is the application of technology by which access to food, energy and water may be addressed in one process: a way to transform waste streams from fossil fuel production into food, clean energy and potable water.
Countries that have implemented large-scale renewable projects have experienced problems on their grid due to intermittency. As the renewable power generators inject power on to the grid, but then quickly remove power from the grid due to intermittency, thermal plants must burn fossil fuels more inefficiently to maintain supply. The intermittency of renewables will actually cause fossil fuel usage to rise. SPL has developed a process to use molten salt heat storage to allow renewable power sources to work with existing power sources to provide baseload power. It has done this by adapting a traditional thermal power boiler to heat molten salt.
The problem facing renewables is not the production of power, but the storage of it. Molten salt can be the “battery” for renewables. SPL’s concept is to store heat in conjunction with the renewable power source. The stored heat can then be used to generate electricity when the renewables are no longer contributing power to the grid. SPL’s design modification to a traditional boiler using the molten salt is both simple and revolutionary.
The process begins with a conventional coal boiler designed with drainable tubes in order to meet the needs for working with salt. This is important because below 250°C, the salt freezes and expands. There are two types of heat transfer surfaces used in salt furnaces that are exactly like their boiler counterparts: First, the membrane wall; and second, the economizer.
All of the heat transfer surfaces in the salt furnace are single phase, which eliminates the need for steam drums, which greatly minimizes weight and the need for structural support. SPL has found that the circulating fluidized bed (CFB) works best due to the capability to have a compact heat transfer surface with the finned economizer. With a bed temperature less than the fusion temperature of the coal, this will result in a lower overall pressure drop and smaller heat transfer surface.
The use of a CFB boiler allows better economy of the boiler due to recovering more heat from the flue gas. The CFB allows a less aggressive means of cooling, which prevents condensation or acid formation on the heat transfer surfaces. This also allows for a 40% reduction in induced fan power compared to a conventional boiler. Based on the design considerations above, modifying a traditional boiler design to a salt furnace simplifies the design process as well as material selection.