Lead Performer: Mainstream Engineering Corp. – Rockledge, FL
Partner: National Renewable Energy Laboratory – Boulder, CO
DOE Total Funding: $199,874.45
FY20 DOE Funding: $199,874.45
Project Term: June 28, 2021 – March 27, 2022
Funding Type: Small Business Innovation Research (SBIR) Phase 1

Project Objective

Growing concerns regarding the impacts of CO2 emissions and climate change have prompted both states and the federal government to promote the adoption of renewable energy sources. Combined with rapidly decreasing costs, the share of intermittent renewable energy generation on the grid, such as wind and solar, has increased rapidly. These intermittent energy sources do not necessarily align with periods of high electric demand, putting additional stress on the grid and requiring electric utilities to relay on high-cost, short-term, fossil-fuel power generation during peak demand. Furthermore, excess renewable generation capacity exists during specific periods, leading to curtailment of these resources. No significant grid-level storage technology has yet gained traction so utilities are attempting a market-based approach to shift electric demand away from peak periods with Time-of-Use (TOU) pricing. Consumers can easily shift some electric loads to off-peak periods, but heat and cooling (HVAC) systems must run at specific times of day when climate control is required. HVAC systems are the single largest electrical load for most residential and commercial customers. As a result, they are not able to effectively able to shift their electrical usage and take advantage of TOU pricing.

Mainstream and our partners at the National Renewable Energy Lab (NREL) will develop and demonstrate a low-cost thermal energy storage heat exchanger using water as a phase-change material (PCM). This PCM heat exchanger (PCM-HX) can be integrated into existing residential and commercial scale HVAC systems and will be produced with advanced materials and manufacturing techniques. During periods of low electrical demand, where prices are low, the system will be charged by freezing the water in the PCM-HX. During high demand periods the PCM-HX will be discharged, significantly reducing the electrical power required by the integrated HVAC system. This product will allow the consumer to shift their electrical usage to off-peak periods and take advantage of lower TOU prices.

Project Impact

Adoption of this HVAC thermal storage technology will have significant benefits to individual consumers, grid stability, and the further adoption of intermittent renewable energy sources. Integrating this thermal storage scheme into HVAC systems using either the Thermal Energy Storage Subcooler (TESS) and the Integrated Two-Phase Pump Loop (I2PPL) design will increase the cost on the order of $800 to $2,500, representing 20 to 60 percent increase in the cost of a new HVAC systems. This additional cost could have a return on investment as low as two to four years depending on the TOU rates, which are only likely to become more advantageous in the future. While not directly comparable to battery storage, this is a significantly cheaper option for load-shifting compared to pure battery storage, which can cost on the order of $10,000 for even the most basic/low-capacity systems. This technology could allow low-to-middle income households to participate in the green energy revolution that has thus far been limited to those who can finance solar and battery systems costing tens of thousands of dollars.

Additionally, shifting electrical loads will reduce the increasing costs incurred by utilities and customers due to peak electrical demand and the effects of intermittent but low-cost energy sources, benefiting all users. Finally, it has been shown that energy storage will be required for adoption of significant percentages of renewable energy generation, particularly approaching the 2030 California 50% RPS. This will become increasingly important as the nation and world attempt to limit carbon emission in the coming decades. This Phase I effort will develop and demonstrate of the novel PCM-HX that can be integrated into either the TESS or I2PPL schemes to achieve load shifting.


DOE Technology Manager: Fredericka Brown
Lead Performer: Jeffrey Milkie, PhD, Mainstream Engineering