Weibin Ma

A temperature-based model for estimating monthly average daily global solar radiation in China.

Since air temperature records are readily available around the world, the models based on air temperature for estimating solar radiation have been widely accepted. In this paper, a new model based on Hargreaves and Samani (HS) method for estimating monthly average daily global solar radiation is proposed. With statistical error tests, the performance of the new model is validated by comparing with the HS model and its two modifications (Samani model and Chen model) against the measured data at 65 meteorological stations in China. Results show that the new model is more accurate and robust than the HS, Samani, and Chen models in all climatic regions, especially in the humid regions. Hence, the new model can be recommended for estimating solar radiation in areas where only air temperature data are available in China.

Preparation and Performance Testing of Composite Adsorbents for Solar Adsorption Refrigeration

In order to develop a high-performance adsorbent for solar adsorption refrigeration, a series of composite adsorbents is prepared by impregnating CaCl2 into the pores of silica gel. Seven samples are prepared using various concentrations of CaCl2 aqueous solutions. Sorption properties of the samples are tested with gravimetric method. The test results indicate that both the adsorption amount and adsorption rate of the composite adsorbents increase significantly compared with that of the pure silica gel. The water uptakes of silica gel and composite adsorbent are 1.96 and 8.08 kg/100 kg adsorbents, respectively, with the relative humidity of 20% and adsorption time of 20 minutes. Subsequently, a novel solar adsorption chiller is designed, in which the composite adsorbent is used as an adsorbent and water as a refrigerant. Performance testing of the adsorption chiller shows that the cooling capacity, specific cooling power and coefficient of performance are 1.03 kW, 128.3 W/kg and 0.27, respectively, when hot water temperature, cooling water temperature and circulation time are 90 °C, 35 °C and 15 minutes.

Preparation of ammonia adsorbent by carbonizing and activating mixture of biomass material and hygroscopic salt

We put forward a new and ingenious method for the preparation of a new adsorbent by soaking, carbonizing and activating the mixture of hygroscopic salt and biomass material. The new adsorbent has high porosity, uniform distribution and high content of CaCl2, and exhibits high adsorption performance. The ammonia uptake and specific cooling power (SCP) at 5 min adsorption time can reach as high as 0.19 g·g−1 and 793.9 W·kg−1, respectively. The concept of utilizing the biomass materials and hygroscopic salts as raw materials for the preparation of adsorbents is of practical interest with respect to the potential quantity of biomass materials around the world, indicating that there would be a new market for biomass materials.

Thermodynamic parameter matching ability of geothermal flash-binary power system

Based on the numerical simulation, the effect of geothermal water temperature on net power output, thermal efficiency, and optimal temperature of flash-binary power system was discussed in this paper. The simulation results show that when the temperature is 80 °C, the net power output per geofluid is about 1.08 and 0.86 kWh/t by direct cooling and indirect cooling of flash system, respectively, when the temperature is 150 °C, the values are 6.57 and 6.35 kWh/t; the optimal temperature of the combined system is 80 °C and 85 °C, 100 °C and 115 °C, and 125 °C and 140 °C by direct cooling and indirect cooling of flash system, respectively, when the geothermal water temperature is 100 °C, 130 °C, and 150 °C. In addition, the power output of flash-binary system by direct cooling is dominated by flash power generation, while by indirect cooling is dominated by binary power generation. The flash-binary power system could provide technical support for geothermal resource utilization in China.

Electricity Generation from Abandoned Oil and Gas Wells

The objective of this study is to demonstrate the feasibility of acquiring geothermal energy using abandoned oil and gas wells. The equations of fluid flow and heat exchange were developed and solved by numerical methods. Computational results indicated that the two main factors of influencing heat exchange and output power were fluid flow rate and geothermal gradient. The net output power is 59.41 kW at a geothermal gradient of 45°C/km and flow rate of 0.04 m/s. The fluid outlet temperature after 10 years of operation is just 0.41°C lower than that of initial time.

Solar radiation on vertical surfaces for building application in different climate zones across China

The global concerns about energy consumption and environmental sustainability elevate the aspiration of applying solar energy to buildings. The information of solar radiation on the building envelope is important in designing the solar devices for building application. In this study, the solar radiation on the vertical surfaces in five major climate zones of China, viz. hot summer and warm winter, mild, hot summer and cold winter, cold, and severe cold, is investigated using the Klein and Theilackers model with monthly average solar radiation measurements on a horizontal surface during 1971–2000. Guangzhou, Kunming, Wuhan, Beijing, and Harbin are selected as the representative cities in the five climate zones. The results show that the peak values of the total solar radiation on the vertical surface in each month occur at different orientations with the azimuth angles during ±90°. For annual utilization, the vertical surface due south is best for the five representative cities, and the deviation in azimu...

Thermodynamic Performance of Ammonia Water Power Cycle (AWPC)

This paper introduces the ammonia water power cycle and presents the cycle performance criteria such as net power output, net power energy per ton of geothermal water, heat efficiency and heat exchanger area of per net power. The cycle influencing factors such as ammonia concentration, solution circulation ratio and hot water temperature are analyzed. Results show that there is an optimum range of ammonia concentration and solution circulation ratio. The power system exploits a new way for utilizing the mid-low temperature heat resource efficiently.

Studies on an Ammonia-Water Compression-Absorption Cooling System (CACS) Drived by Solar Energy

An alternative method using the ground heat exchanger to provide cooling water for a solar-driven CACS is proposed with the aim to improve the performance. Using a mathematical model developed in this study, theoretical analyses are carried out to investigate the performance of the combined system. The results show that with an additional compressor, the system can be driven by 50¡æ hot water, and the pressure ratio has obviously effect on the cooling capacity. These make the system can operate with the flat-plate solar collectors and fit for variable cooling demands. The effects of driving temperature on the system performance are also investigated.