Combined Heat and Power (CHP) Microgrids


Montgomery County, MD

Combined Heat and Power (CHP)

Reliability and weather risks, along with the desire to reduce emissions, reduce energy costs, and achieve aggressive sustainability goals, were the driving factors behind this microgrid project. A microgrid is defined as a small network of electricity users with a local source of supply that is typically attached to a centralized national grid but is able to function independently. GMS was part of a larger team who developed and installed advanced microgrids at Montgomery County Public Safety Headquarters and Montgomery County Correctional Facility. Both projects feature microgrids based on Combined Heat and Power (CHP) systems incorporating solar energy. Montgomery County decided to focus on these facilities because they are essential to the continuity of public services, especially during disasters or other events when those services are needed most.

The Public Safety Headquarters

The Public Safety Headquarters (PSHQ) is the county’s primary administrative hub for a range of critical public services. It houses much of Montgomery County’s transportation management resources, components of the county’s Office of Emergency Management and Homeland Security, Fire and Rescue Service headquarters and a police station serving much of the central part of the county. The building’s infrastructure was nearly 50 years old and needed upgrading. It presented an opportunity to launch the microgrid initiative to address the aging infrastructure while improving the facilities overall capabilities and sustainability while meeting the county’s budget. The PSHQ mircrogrid incorporates nearly 2MWdc of canopy-mounted solar energy capacity, providing shade to cars while powering the facility. A new 865 kW CHP system replaced two existing generators providing baseload energy supply to the facility. Of the four original generators on the site, one was repurposed to another county facility; one was sold as surplus; and two were retained to provide additional redundancy. The CHP system produces hot water to heat the building and domestic hot water as well as for use in an absorption chiller that supplements existing building chillers. Collectively the PSHQ microgrid provides an estimated 90-95 percent of the facility’s annual electricity consumption. It will reduce county greenhouse gas emissions by over 3,000 metric tons annually, equivalent to taking 680 cars off the road.

The Montgomery County Correctional Facility

The Montgomery County Correctional Facility (MCCF) in Boyds is the site of the second microgrid project. The facility is responsible for the custody and care of approximately 1,000 inmates. The MCCF microgrid project expands the facility’s power generation capabilities by adding a 220 kW CHP system to its existing generators. The system can produce hot water used on-site for space heating and potable water heating. The CHP system combined with a 2.8 MWdc of on-site solar energy capacity enables the facility to generate 60-65 percent of its electricity on-site. During an emergency, it benefits from advanced controls that enable it to separate from the utility grid and take advantage of the CHP and existing generators to operate in “island” mode.

GMS performed the development, permitting, engineering, design, procurement, construction, interconnection, testing, startup and commissioning of the facility equipment that includes the electrical infrastructure, Microgrid components and onsite power generation equipment at both facilities. GMS was also responsible for the on-site coordination of REC Solar who supplied the turnkey canopy-mounted solar energy system at PSHQ and at MCCF, and was responsible for the integration of that solar equipment into the overall facility design.

Pepco and Potomac Edison were responsible for facilitating approval of the interconnection of both the PSHQ and MCCF microgrids to the centralized grid.