Solar Water Heating for the Residential, Commercial and Industrial Sectors

Solar water heating using aluminum mini-channels has the potential to lower upfront costs for solar thermal installations.

The Regents of the University of California, Merced


Merced, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

This project is completed and the final report has been submitted for review. The aluminum mini-channel solar collectors were installed at a single-family home and a 25-unit apartment complex, both in Southern California. The systems reached efficiencies of 80% during specific periods of the day and performance data collected during a year of operation showed reductions in natural gas use of 34% to 38.8%, respectively (annual savings of 435 therms for the single-family home and 1542 therms for the multi-family building). Additionally, a prototype copper mini-channel
solar collector was fabricated and lab tested at UC Merced. Testing was delayed due to COVID-19 campus restrictions, but preliminary results
showed good potential to produce low-grade vapor at 90 degrees Celsius.

The Issue

Recent natural gas leaks, such as the leak in Aliso Canyon in Southern California, and the continued need to improve air quality in Southern California, have placed a higher priority on reducing natural gas use. Hot water in buildings is one of the primary uses of natural gas. Conventional solar water heating systems displace natural gas, but are expensive and complicated to install. UC Merced researchers previously tested a prototype mini-channel based solar collector for buildings that could compete with conventional systems. Early research results show cost reductions of up to 30 percent, however real world demonstrations are needed to verify performance and system costs.

Project Innovation

The project demonstrates aluminum mini-channel solar water heating collectors on residential single and multifamily buildings in the Los Angeles basin. In addition, copper mini-channel solar collectors, capable of producing low-grade steam for such uses as dry cleaning, steam cleaning, produce drying, sterilization, and blanching of vegetables, will be developed and lab tested at UC Merced. The research will determine if the copper mini-channels can produce steam required for use in such industries. Data is being collected on system performance, cost, and customer preferences of mini-channel solar water heating versus conventional solar water heating technology. Project goals include promoting wider adoption of cost-effective solar water heating technology, and overcoming the technological, economic and market challenges of solar thermal water heating.

Project Benefits

The mini-channel technology has the potential to reduce the upfront cost of solar water heating collectors and thus increase market penetration of this technology. Replacing natural gas-fired systems with solar water heating will reduce natural gas use and greenhouse gas emissions, especially for residential water heating and industrial processes.

Lower Costs


This project aims to lower the upfront cost of solar thermal water heating systems by up to 30 percent by utilizing lower cost materials and increasing the efficiency of solar collectors utilizing aluminum in collector construction. The reduction in natural gas consumption will also lower ratepayer utility bills.

Environmental & Public Health

Environmental Sustainability

This project aims to improve air quality and reduce greenhouse gas emissions by reducing the consumption of natural gas for water heating.

Key Project Members

Project Member

Gerardo Diaz




The Regents of the University of California, on behalf of the San Diego campus


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