Ground-Source Heat Pump Performance Enhanced with Earth Charging by Means of Solar-Cooker-Style Thermal Collectors, Leading to Zero Carbon Emission

This paper reports on an experimental augmentation system for ground source heat pumps using solar-cooker style panels to recharge the ground, thermally. This is running experimentally on a house in Nottingham, England. The house has 4 kW of Photovoltaic on the roof., and a ground source heat pump for heating and hot water, using twin 48 metre boreholes. Direct and Interseasonal Solar charging is a way to prevent the progressive frosting of the deep ground, and measured over a year, it can improve the GSHP performance by up to 20%. The solar ‘sunboxes’ in Nottingham are directly plumbed to the ground loop, and are thermostatically activated. In Winter and Equinox they provide diurnial benefits to the GSHP. During the Summer, they deposit abundant amounts of free heat into the deep earth. They do not suffer from ‘stasis’ as the deep ground has non-finite capacity. With the improved COP and other efficiency measures, the heat pump has worked at a 33% reduction of its previous electrical consumption. The photovoltaic roof generates 3,250 kWh, and the key performance indicator of the experiment has been to reduce GSHP consumption to that figure, making the house Carbon emission free. The key indicator is that since installation, the deep soil has never fallen below 10 ºC at the lowest ebb of winter 2010-2011. Full details of the project are visible at http://chargingtheearth.blogspot.com