Commercial System Design: Ground Sourced Heat Pump, Buildings Heating and Cooling Pumps
The design procedure is a critical part of the geothermal system, a poorly designed system can have adverse effects of the whole performance. GeoPro design prides itself on taking every care during this process, the steps are as follows:
1. Determine the buildings heating and cooling loads
The complete design of a buildings heating and cooling system involves several steps. Each is important to a satisfactory system performance. However, the heating and cooling loads estimates are the most critical as everything else in the system is dependent on them. The most basic load calculations are referred to as design loads, energy and ground loads are also considered
- Design Loads are used to size and select equipment for a system and to design the heating/cooling system accordingly. Design loads are based on standard or accepted conditions for a given location.
- Energy Loads are used in predicting the energy necessary to operate the system for a set period of time. The basic calculation methodology may be the same as design loads; however the, actual operating and weather data are used.
- Ground Loads are associated with GSHP and relate to the design of the ground heat exchanger coupling device. In principle, these calculations are similar to energy loads except the ground load is the heat rejected to the ground (cooling mode) or removed from it (heating mode).
2. Select a properly sized ground sourced heat pump
Sizing the heating/cooling equipment for a system is fundamentally the most important step in the design process. For residential systems, the equipment is usually the unit type (a matched set of components designed to serve as a whole); once a unit is selected, a number of parameters are fixed or have little or no room for adjustment. For example, a unit is designed for a nominal airflow rate in a ducted system, and only a small adjustment is possible.
A water sourced heat pump is no exception, its designed for a limited range of water flow rates. Therefore, other parts of the system such as under floor circuits (or ducted system), ground heat exchanged and brine circulation pump must match the requirement capacity of the heat pump.
3. Select the distribution system
This is another critical part, as depending on climate conditions and humidity levels some systems would be totally unsuitable. Care must be taken in order to achieve heating and cooling requirements.
4. Estimate the buildings energy requirements
This is calculated from the following data:
- Buildings heating and cooling loads.
- Heat pump size and type.
- Climate and soil conditions.
5. Estimate the ground heat exchanger loads
The design of the ground couple heat exchanger for a ground source system requires information regarding the amount of heat transferred to our from the ground during a specific period of time. Usually the warmest and coldest months of the year are adequate.
During the cooling season all energy inputs to the system must be rejected to the ground. During the winter months heat is removed from the ground in an amount equal to the unit capacity minus the electrical power input.
