Case Study 1

Massachusetts Operator.

 

Project Issues

Greenhouse operations in MA require thermal energy during more hours of the day than other similar greenhouse grow operations in locations such as California

The ratio of recovered heat to power output of a given sized combined heat and power (CHP) system does not provide for sufficient thermal energy if CHP is sized properly to satisfy the electricity demand

Each greenhouse utilizes significant supplemental lighting, but peak Demand Charges are not high enough to justify energy storage as a stand-alone service

National Grid allows for the export of power on an “avoided cost” basis that varies with instantaneous grid-wide demand for power

National Grid provides grants for distributed generation systems interconnected with their grid up to 5 MW

Alternative Energy Certificates (“AEC”s) have significant equivalent kWh value (converted from recovered heat); the calculation of which is particularly favorable to combined heat and power solutions

Customer-Specific Solution

The facility is designed to fully utilize thermal energy for both heating and cooling

  • A combined heat and power solution was specified that was sized to the total thermal energy required by the facility at its peak need

  • The result was a CHP system that:

    • Was sized approximately 33% larger than the peak electricity demand of the grow facility

    • Recaptures 100% of the heat during the operational hours of the facility, maximizing the creation of AECs

    • Exports Up to 5 MW of power to the grid, especially during hot summer hours when the grid value is highest — typically there is more than adequate sunlight for the greenhouse at these times

    • Benefits from a significant local support from the utility and state

Lessons Derived:

This project configuration shows that grow operations in Massachusetts benefit greatly from the maximization of thermal energy usage and the oversizing of systems to satisfy maximum thermal demands. The AEC is particularly beneficial to high-overall-efficiency CHP systems and the combination of a Distributed Generation tariff with available grants and high TOU power costs during the summer months makes such a configuration repeatable. The Massachusetts electricity markets also have strong incentives for solar and storage technologies. Indoor grow operations would likely include both solar and storage to further improve economics.