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This paper discusses the performance of a solar assisted ground source heat pump (SAGSHP) system used for storage of solar energy in day time and space heating at night. Experiments were conducted to estimate the effectiveness of solar energy storage under the ground using a U-tube ground heat exchanger by absorbing solar energy from 9 A.M. to 5 P.M. and utilize the stored energy during space heating in the night time from 7 P.M. to 3 A.M.. Using the experimental data, heat absorbed by the solar collector, heat injected into the ground, heat extracted from the ground and COP of the system have been computed. Results indicate that heat absorption by the solar collector varied from 2.07 to 2.56 kW with increase in mass flow rate. Due to heat losses, only 1.991–2.414 kW of solar heat could be injected into the ground in the day time. Increase in mass flow rate of heat transfer fluid in the collector and ground heat exchanger has resulted in 21% increase in heat injection into the ground. Due to charging of ground, thermal energy of 2.8–3.2 times the work input to the solar collector could be extracted additionally from the ground in the night time for space heating. Charging of ground has resulted in 23% increase in the COP of the system for space heating in the night time. [ABSTRACT FROM AUTHOR]

• Community-led solar energy projects in India are analyzed using the grassroots innovation literature. • The status of community energy projects in the US, Europe and India and presented. • Three case studies, namely DURGA, Barefoot College and Rampura solar project, are reviewed. • Case studies are consistent with social justice concerns, such as participation, equitable distribution of benefits and recognition of marginal communities. Sustainable technologies for social mobilization and community empowerment are contemporary phenomena of grassroots innovation movements. The origins of the grassroots innovations appear in the appropriate technology movement of the 1970s, the People's Science Movement of the 1980s, and more recently, the Social Movement Organization as seen in the cases of the Honey Bee Network in India and the Social Technology Network in Brazil. This paper articulates the community energy movement in India in the framework of 'grassroots innovations for sustainability'. The paper presents three fine case studies of off-grid community energy initiatives namely, the Dungarpur Renewable Energy Technologies Private Limited, (DURGA), the Barefoot College and the Rampura Community Solar Power Plant (CSPP). The case studies represent three different kind of business models of community energy projects – a private limited company, a market-based model and a village energy committee (VEC) model. Therefore, they are representative of different grassroots innovations in off-grid energy projects. The case studies exemplify how off-grid community energy projects may manifest an embedded character of the grassroots innovations and address energy poverty and social justice concerns, such as community participation, equitable distribution of benefits, representation of marginalized communities. The case studies also demonstrate that the grassroots innovations in off-grid energy projects may enhance social mobilization, community empowerment and sustainability. To conclude, the findings of this research show that grassroots innovations in technology and sustainable development are consistent with each other. [ABSTRACT FROM AUTHOR]