Boa Vista Apartments is an elderly high-rise development, comprised of ninety-nine (99) one-bedroom apartments with a community room and a kitchen. It also is the location for the main administrative offices of the New Bedford Housing Authority. The development is owned and operated by NBHA. Since energy costs are a large portion of its operating budget (40% across all its facilities), NBHA has continually looked for ways to reduce energy expenditures.
Through its energy performance contract with Constellation Service Company, NBHA selected project developer Aegis Energy Services (Holyoke, MA) to conduct a feasibility study for reducing energy costs with a combined Heat and Power (CHP) system at Boa Vista. The feasibility study showed that Boa Vista was a good candidate for CHP and it would save NBHA nearly $400,000 over ten years.
NBHA and Constellation Energy Services contracted with Aegis Energy Services to engineer and install one turnkey 75kW packaged CHP system to provide both electricity and hot water to the multi-unit building. Aegis Energy Services also agreed to apply for an $18,00 rebate from NStar, the Massachusetts-based electric and gas utility, on behalf of NBHA.
The CHP system, designed and installed by Aegis Energy Services, consists of one Aegen ThermoPower 75LE Cogeneration Module, which features a natural gas-fired engine supplying 75 kW of electricity. The main electrical distribution panels in the building receive the cogenerated electricity, which is then distributed to met 52% of the total building load. Electricity from the grid services the remaining load.
The system is supplied with a state of the art Windows-based microprocessor for automatic, unattended, and remote monitoring operation by Aegis Energy to ensure its is operating properly.
Use of Recovered Heat
Heat contained in the Aegan ThermoPower unit’s engine and engine exhaust is captured through various heat exchangers located in the oil cooler, engine jacket, and exhaust gas manifold heat exchangers. This captured heat is then transferred to Boa Vista’s comfort space and domestic hot water heating loops. The CHP system meets 74% of the building’s total space heating needs and 100% of domestic hot water needs.
Maintenance and Operational History
The Aegan ThermoPower unit was installed and began operating in 2009, and has been running twenty or more (20+) hours per day. NBHA contracted with Aegis Energy Services to maintain the CHP system that includes remote monitoring of the system around the clock. This monitoring allows Aegis to detect and correct any disturbances and other system problems before they can impact the savings from the CHP system. Maintenance costs average $5,000 annually.
Costs and Benefits
The initial cost to install the Boa Vista CHP system was $196,000, which includes the rebate from NStar. Overall, Boa Vista will save $34,000 in the first year in energy operating costs (after fuel and maintenance costs), or a 25% reduction in energy costs. These savings steadily increase over the ten year analysis period. The project is expected to generate a ten year net operating savings of nearly four hundred thousand dollars with a simple payback of six and a half years.
End User Perspectives
Looking to the future, NBHA has plans to install Aegis Energy Services CHP systems in other multi-family housing developments and provide some energy to nearby schools and recreational facilities. The NBHA believes that if these cogeneration systems prove to be successful, then this model may be repeated at other Authorities.