Lowell
Massachusetts, USA - Ground-source heat pump
Summary
Space conditioning control is critical for many quilt displays. A standing column geothermal heat pump was installed when this historic building, the New England Quilt Museum, was renovated and the former natural gas and electric systems replaced. The museum was designed for maximum heating andcooling loads of 211 kW (60 tons) . Prior to the retrofit the building was analysed for the geothermal heat pump feasibility and economic advantages. The wells are located under a nearby parking lot. The seasonal performance factor (SPF) of the heat pump is about 4.2.
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Building and design values
| Building type: | Museum | |||
| Location: | Lowell , Massachusetts, USA | |||
| Year of construction: | 1919 | |||
| Number of storeys: | 3 | |||
| Heated floor area (m2): | No data | |||
| % of total floor area (%): | No data | |||
| Design outdoor temperature (ºC) | Heating: | No data | Cooling: | No data |
| Design indoor temperature (ºC) | Heating: | No data | Cooling: | No data |
| Degree days | Heating: | 4 230 | Cooling: | No data |
| Base temperature for degree days (ºC) | Heating: | 18 | Cooling: | No data |
Heating and cooling
| Application: | Space heating and cooling | |||
| Heat pump type(s): | Water-to-water | |||
| Heat pump installed capacity (kW) | Heating: | 215 kW (6x35) | Cooling: | As heating |
| Refrigerant: | R22 | |||
| Heat source | Groundwater | |||
| Details: | See additional information | |||
| a) Type of ground heat exchanger: | Standing column well (2) | |||
| b) Borehole depth (m): | Column depth 457 (1500 ft) | |||
| c) Pipe length (m): | No data | |||
| d) Heat transfer fluid: | Water | |||
| e) Flow rate (l/h): | No data | |||
| Distribution system(s): | Fan coils | |||
| Supply and return temperature (ºC) | Heating: | 55/45 | Cooling: | - |
| Auxiliary system: | No data | |||
| Heat pump design: | No data | |||
| Supplementary system: | The existing gas boiler has remained in place as a backup for the winter season. It has not been required since the retrofit. | |||
| Heat pump system completion date: | Early 1995 | |||
| Additional information | ||
| The heat pumps are on a simplified control scheme. The existing pneumatic control system was and remains non-functional. The building loop water temperature is manually set and automatically controlled by two aquastat controls. The aquastat controls are set with an approximate 2ºC (7 F) differential between 'call' temperatures. Each of the two banks of the three heat pumps is sequentially called by the temperature differentials. After the first heat pump, for example, 1 or 4 is called, the subsequent heat pumps within that 3-unit bank are called by set time delays. As the first bank is called, the first standing column well pump starts and water flows simultaneously through all three heat pumps in that bank. |
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If the first bank cannot satisfy the building loop temperature and the building water loop falls more than 2ºC (7 F), the second bank is called. The second bank starts the second well pump, the large twoway motor valve opens and the water flows through all six heat pumps and the heat pump 4 starts, with 5 and 6 following within 3-8 minutes. |
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Performance
| Energy | Energy savings are over 60%. |
| Coefficient of performance (COP) | |
| Heating: | About 4.2 |
| Test conditions: | Seasonal performance |
| Heat pump cost breakdown | |
| Heat pump only (USD): | 215 000 total cost of heat pumps and wells |
| Installation (USD): | |
| Capital cost (excluding heat pump) (USD): | |
| Maintenance: | No data |
| Alternative system (if has been considered) | No data |
| Fuel cost | No data |
| Payback | No data |
| CO2 emissions | No data |
| Operational experience and other comments | ||
| The manual on-off control of the heat pumps and the thermal inertia of the building have created long periods without heat pump operation. These allow the standing column wells to 'recover' more than typical installations. However, when the heat pumps are in operation these periods tend to be longer and the wells at higher temperatures. |
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Water-to-water heat pumps are preferential for retrofits. Older buildings often have oversized air handlers and radiation. Water-to-water heat pumps can be operated at smaller evaporator-to-condenser temperature differences, increasing the efficiency. Expensive or complex control systems are not required. Small commercial retrofits with existing electric or fossil heating and chiller cooling can achieve attractive savings. The annual total building operational costs can reduce by 50-65% if geothermal heat pumps are used. |
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Contacts
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Contact 1: |
John Logan |
| Company: | Water Energy Distribution |
| Role: | System design |
| Address: | 15 Wawenock Road Raymond, Maine 04071 USA |
| Telephone: | + 1 207 655 7529 |
| Fax: | + 1 240 414 8924 |
| Email: | geomaine @ maine.rr.com |
| Last updated: 1 March 2004 |
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