In 2013, Walgreens installed it’s first net-zero energy store in Evanston, Illinois. The store has a transcritical CO2 and geothermal heat pump system, which uses ground water to heat and cool the store, with reported energy savings of over 60%. Its Empire State Building store uses a split mini-rack system that employs a zero-ozone depleting refrigerant.
A study on refrigerants used in geothermal heat pumps in a 14-storey residential building in Iran, has shown that ammonia and hydrocarbon produce significantly better Coefficients of Performance (CoP) when compared to HFC-134a and HCFC-22.
The researchers monitored performance of a horizontal closed-loop ground heat pump with a cooling load of 915 kW (260 TR) in the town of Qazvin. Ammonia came out as the most energy efficiency refrigerant with a CoP of 4.663. Hydrocarbon, n-butane’s COP was 4.606. Overall the natural refrigerants had COP’s 4.5%-5.8% higher than HFC134a. Similar results were obtained for open-loop and vertical closed-loop ground heat exchangers.
The study also found ammonia and n-butane to have a reduced initial system cost compared to HCFC-22 and HFC-134a in terms of initial system cost.
The heat pump has a heat output of 8.25kW and a cooling capacity of 5.52kW. It has heating outlet temperatures of upto 70°C, enabling combination with conventional radiators. It is PV ready, with performance adjutsable to solar power availability
The propane heat pump uses the ground as the source energy and can be used in combination with photovoltaic systems, increasing the annual efficiency. Worldwide heat pump remore control access via the internet is also available for this system.
