HVAC
The design approach for the mechanical systems in Team Alberta’s SolAbode was rooted in the following principles:
- energy savings shall not result from reductions in thermal comfort or indoor air quality (IAQ)
- the use of off-the-shelf components will illustrate the potential of today’s technology, with proven reliability and support infrastructure, for energy-efficient system designs
- where possible, components should be multi-purposed and integrated to maximize overall system performance, capitalize on synergistic opportunities and reduce the number of pieces of equipment.
The resulting design uses a water-source heat pump as the central piece of equipment to provide space heating and cooling as well as domestic hot water heating (during cloudy periods or at night when the solar thermal system is inactive). Space heating and cooling is done with a forced air system, ensuring rapid response and a high level of control. Ventilation is done with an energy recovery ventilator.
Put simply, a heat pump moves heat from one place to another. In the SolAbode, the heat pump interacts with two large tanks of water. One acts as a heat source (energy is removed and used to heat the house or heat water) and the other a heat sink (heat is removed from the house and ‘dumped’ in the tank).
The solar thermal system is coupled with the heat source tank, termed the thermal storage tank. This integration increases the efficiency of both the solar thermal system (by lowering the approach temperature to the panels) as well as the heat pump (by increasing the approach temperature to the heat pump when in heating mode).
Thermosyphons are coupled with the heat sink tank, termed the ground tank. These passive devices reject heat to the air at night when the air temperature drops below that in the tank. Similar to how the heat pump efficiency is increased when the working fluid temperature is high, the efficiency is also increased in cooling when the working fluid temperature is low. The use of thermosyphons helps to achieve this goal.
Tying the HVAC together is an advanced control system that continuously monitors all the components as well as the indoor and outdoor conditions (temperature and humidity). The control logic seeks to maximize the overall system efficiency. Additionally, the system logs energy use data and is able to report back to the homeowner their use patterns, which can result in savings opportunities. Lighting, external blinds and home entertainment are also tied into this system through the SolAbode’s home automation system.