Mixed technology BEMs ( Building Energy Management ) case study 3
Customer has 8.3 kWp of solar, hot tub, irrigation system and air source heat pump (ASHP) serving a mixture of underfloor and radiators. A large amount of the solar is being exported and the ASHP has suffered two compressor failures in last four years causing significant replacement costs.
Investigation
An I2W, and a heat meter was installed monitoring the ASHP, the house load and import/export to the grid.
Comment
The major consumption, in particular the ASHP, did not coincide with the solar day giving rise to a large export during the day and a large import during evening and night. The ASHP was short cycling with its COP (heat output/Electrical input) being very low. In addition, the backup heaters at low temperatures did not function. This generated significant unnecessary running costs in addition to hardware replacement costs.
Recommendations
Replace ASHP backup heaters and determine correct flow and return temperatures.
Install an I2W to control the hot tub maximizing solar input whilst still maintaining temperature.
Install second I2W to add solar power to hot water supplementing ASHP
Install a battery storage system
Install a BEMs controller to control ASHP, control valves of the underfloor and radiator zones, the irrigation system, the I2W controllers, heat meter and energy storage
Develop a custom cloud and local display to show status allow control and collect performance data.
Results
The ASHP flow and return temperatures and the radiator valve settings have been correctly optimized to maximize COP and minimize short cycling giving a dramatic drop in consumption costs and the compressor loading with the effect of significantly extending its life, thus delaying further hardware replacement costs.
The hot tub achieves desired temperature with about 50% coming from solar
The hot water is largely supplied by solar for 9 months of the year.
The BEMs controller now controls the whole system with a local dashboard and remote logging/control fault reporting.
The battery storage system reduces the export during solar day and the import at night.
For a large part of the year 100% of the solar is used.
Public dashboard for the installation