Solar Combined Energy Systems for Space and DHW HeatingDescription

Project Leader

• I. Beausoleil-Morrison

Description

Currently, with the exception of pool heating, virtually all-residential solar thermal installations in Canadian housing are for heating domestic hot water (DHW) for potable water applications (e.g., washing and bathing, etc.). These systems use short-term thermal storage to store energy over hourly or daily periods (i.e., diurnal thermal energy storage) and therefore rarely achieve solar contributions above 60% of the DHW load (Dinçer & Rosen, 2002). This limits their energy contribution and also does not address space heating demands that account for 67% of the total building energy consumption for the existing Canadian housing stock (Natural Resources Canada 2009)xii. There is potential to increase the contribution of solar energy for both DHW and space heating by increasing the size of solar collector arrays and through the use of medium capacity (i.e., medium-term) thermal storage systems that can store sufficient energy for three to five days. These systems, commonly referred to as “combi-systems”, are most common in Europe (Hadorn, 2008a). In Canada, however, little research has been conducted on the applicability of these systems for Canadian housing or climatic conditions. In particular, due to Canada’s more severe winters, larger solar collector arrays would be required to significantly contribute to the space heating load. This has drawbacks, as much of the solar capacity would not be utilized during the summer, leading to poor economic performance and possible overheating that could accelerate degradation or scald occupants. Therefore, there is a need to optimize the configuration of solar combi-systems to avoid over-sizing while maximizing the utilization of solar energy. The optimum design of a thermal storage for a combisystem depends on many factors, including the temporal distribution, magnitude and temperature of the solar energy supply and of the thermal loads. The variation of the load throughout the day and season, the required charge and discharge rates, and the spatial limitations related to the installation and placement of the storage must also be considered (Weiss, 2003). Moreover, the sizing and orientation of the solar array and overall system control are important considerations. Such considerations dictate the need for accurate simulation methods that concurrently model the dynamic thermal loads of the building as well as the full complexities of solar collectors, thermal storage, and other system components. Moreover, limitations in state-of-the-art building simulation and system simulation tools preclude an accurate treatment of innovative concepts such as hybrid active-passive systems that combined thermal storage in the building envelope as well as active stores. 

Sub-Projects

• 1.2a Development and evaluation of cost-effective multi-tank storage
• 1.2b Optimization of combi-systems for Canadian conditions
• 1.2c Solar assisted heat pumps

Back to Theme I : Integrated renewable energy systems and heating/cooling systems for buildings