UCLA

Thermal energy storage (TES) provides increased flexibility to residential and commercial customers in the operation of their combined heating and power (CHP) systems by separating generation of electricity from heating or cooling load. TES systems that can store high temperature exhaust heat (up to 600�C) from natural-gas powered CHP, such as low-cost elemental sulfur-based technology developed by UCLA researchers, can dramatically improve system economics. TES with quick heat response allows more commercial buildings with varying thermal and electrical demand to benefit from CHP.

In this thesis, realistic hourly electrical and heat usage data, along with energy pricing and installed system costs, were used to give insights into key economic indicators about the viability of CHP-TES systems for various commercial building types in Los Angeles, CA. The metrics used to understand the value of adding TES to existing CHP systems and new CHP-TES systems included upfront costs, payback period, and lifetime value for different capacity sizing of TES.

The results showed that adding TES to baseload CHP systems improves the lifetime value of the plant with a payback period of less than five years for many commercial building types. The large hotel building type offers the shortest CHP payback period of 2.8 years and TES retrofit payback period of 1.6 years. The value of the TES system to the end user can be more than 10 times the initial cost of the TES over a 15 year lifetime. Further, a sensitivity analysis of the TES cost, utility costs, and weather regions was performed. Accounting for regional variations in electricity prices, natural gas prices, and weather, we found that although electricity usage stays relatively constant, heat usage and TES economics vary greatly by region. Overall, we showed that high temperature thermal energy storage such as based on molten sulfur or molten salt, can efficiently store highly-valuable heat for enhanced small-CHP flexibility, thereby changing the economics of small-scale CHP systems for residential and commercial buildings, and promotes a more level grid from the demand side.