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The hybrid ground-coupled heat pump (HGCHP) systems with supplemental heat rejecter/supplier can effectively solve heat imbalance problems in the subsurface, and consequently improve the operation performance of the geothermal systems. For example, solar energy and/or industrial waste heat may be used as stable heat sources for underground heat storage in northern China with higher heating load, and cooling towers are installed to release heat into the air in southern China, where more cooling demand is needed. This paper reviews and discusses different HGCHP systems, which have been applied in China. And based on the heat transfer model of vertical borehole heat exchangers (BHE) for HGCHP systems, physical and mathematical models of multistage series circuits are developed to illustrate the heat transfer process of the underground thermal storage. A set of parameters, such as borehole spacing, heat recharging rate fractions and thermal properties of soils, which affect the thermal performance of the ground heat exchangers are analyzed, and the optimal solutions are discussed for engineering application. [ABSTRACT FROM AUTHOR]

In the rural area of northern China, residents often use a traditional stove-Kang system to heat their homes, which is an effective way of using locally-produced biomass to solve the energy and environment problems. However, many of these homes are not heated sufficiently during the winter months. The current system is inefficient and requires high levels of fuel consumption. This paper researches the Kang system by creating a simplified and modular system modeling program with the aim to assist in accurate real-time design and optimization of the domestic Kang heating system. This part-1 introduces the structure, principles and the underlying equations of the modular simulation system. A variety of improvement measures were modeled and tested, upon the base model, including the use of a water heat exchanger and radiator system to the existing Kang set up, solar hot water system, bathing system, and the use of phase change material at the surface of the Kang. The program demonstrates good flexibility of implementing different technical solutions as well as fast simulation capability. [ABSTRACT FROM AUTHOR]

Abstract: The intermittent characteristic of a solar-alone or a wind-alone power generation system prevents the standalone renewable energy system from being fully reliable without suitable energy storage capability. In this study, the most traditional and mature storage technology, pumped hydro storage (PHS), is introduced to support the standalone microgrid hybrid solar-wind system. This paper explores a new solution for the challenging task about energy storage. A mathematical model of the hybrid system is developed and the operating principle is introduced. The proposed system is applied in a case study to power a remote island in Hong Kong, and its technical feasibility is then examined. The hour-by-hour simulation results indicate that the intermittent nature of the renewables can be compensated by introducing the PHS technology. Therefore, a reliable and environmentally friendly power supply can be provided. The results demonstrate that technically the PHS based renewable energy system is an ideal solution to achieve 100% energy autonomy in remote communities. [Copyright &y& Elsevier]

Abstract: A reliable supply of energy is essential to maintain and to improve human being''s living conditions. Compared to the conventional coal-fired approach, renewable energy (RE) helps to mitigate the impacts of greenhouse gas emissions to a large extent. As a newly developed sector with large resource potential and good commercial prospects, China''s wind power industry is exceeding expectations. By 2008, installed capacity of wind power in China totaled over 12GW, making China the fourth largest wind market in the world. However, China has to admit the gap with foreign leading countries, mainly in technical R&D for large-scale wind turbine generation units. This paper attempts to formulate an analytical model for studying and assessing factors that have significant impacts on the local industry. An improved dynamic Diamond Model is developed to help the international community to understand the status quo of the Chinese wind power industry. In order to build a stronger wind power industry, the elements identified in the model need to be strengthened. [Copyright &y& Elsevier]