Case Study-Clover


Clover Stornetta Farms, founded in 1970’s and based in Petaluma, CA, is a family-owned and operated dairy processor and one of California’s leading dairy companies. Clover distributes a wide array of top quality dairy products from California’s North Coast throughout California, Arizona and Nevada.

For years Clover has been a pioneer in the dairy industry with regard to sustainability efforts. The company was the first dairy west of the Mississippi to offer rBST free milk and continues to show its commitment to sustainability in its business strategy, product and its dairy producer network of small, family owned farms.

Clover’s local family farms in Sonoma and Marin Counties are committed to sustainability of their land, welfare of their cows and producing the highest quality milk in the country.

Thanks to these efforts, Clover is one of only 13 companies worldwide to be recognized with the Seal of Sustainability™ showcasing Clover’s leadership in the acceptance and adaptation of sustainable economic, social, and environmental business practices.


Dairy production requires a large amount of hot water and Clover Stornetta uses over 6,000 gallons each day for its wastewater treatment processes. Clover has already employed a waste water treatment system which reduces its water consumption by 10 million gallons per year, but sought ways in which it could further its sustainability efforts, reducing energy costs and greenhouse gas emissions.

Clover searched for a renewable energy source that would not only offset its electricity usage but also natural gas consumption during the wastewater treatment process at its processing plant in Petaluma, CA.


Solar cogeneration was chosen as the renewable solution for the plant as it provides Clover with hot water, renewable electricity and a less than a five year payback. This hybrid technology combines the best of both worlds in one product: photovoltaic (PV) and Solar Hot Water (SHW) generation.

The dual energy generation utilizes more of the sun’s energy (75% with solar cogeneration vs. 15% and 60% with PV and SHW, respectively) and provides customers with more energy, better environmental benefits and faster paybacks.

Cogenra Solar collaborated with OneSun, Inc. a local expert in solar PV and solar thermal installations, to construct Clover’s 20-module system on the roof of the Petaluma dairy plant.

The 50.6 kilowatt system, constructed in just a few weeks and taking up less than 1,500 square feet of roof space, integrated seamlessly with Clover’s existing natural gas water heaters and electrical equipment. Cogenra’s SunDeck modules are simple repeating units offering modularity and easy scalability.

The solar cogeneration array pre-heats water to 145 F, for Clover’s steam-fed wastewater treatment process. During the wastewater treatment process, wastewater is pumped continuously through three wastewater filters, which are periodically backflushed with cold and hot water. The Cogenra system pre-heats the water, which is then injected with steam in order to reach the required CIP temperature.

The system was assembled on site and includes fully integrated hydronics, controls and inverters, enabling a plug-and-play, turnkey solution. In addition, remote monitoring and diagnostics provide Clover with insight into the system’s real-time performance.


Cogenra’s solar cogeneration installation provides Clover with financial and environmental improvements for its Petaluma dairy plant, helping reduce not only energy costs but also greenhouse gas emissions.

The system will offset about 15% of the plant’s energy usage, displacing approximately 11,500 kilowatt hours and 2,300 therms annually. This translates into more than 50% savings on energy used for the wastewater heating process.

In 2009, the dairy industry voluntarily committed to reduce greenhouse gas (GHG) emissions of fluid milk by 25% by 2020. The Clover installation will reduce Petaluma plant’s greenhouse emissions by 32 metric tons each year, equivalent to removing 3,500 gallons of gasoline and saving 800 trees annually.

Solar cogeneration helps dairy plants achieve industry environmental goals better than other solar systems, providing greater GHG emission reductions: almost 3 times more than photovoltaics and almost twice than solar hot water systems.