Solar and geothermal energy for low-carbon space heating and energy independence.

In developed countries, space heating is highly dependent on fossil fuels consumption. Also, the non-renewable fuels combustion emits CO2 which is claimed to impact the most on greenhouse effect. The utilization of Renewable Energy Sources (RES) for space heating, instead of fossil fuels, has been found to be feasible for systems’ greater energy independence and reduction in CO2 emissions. Solar Assisted Ground Source Heat Pump (SAGSHP) systems are a promising technology which can be used to accomplish the above framed target. A mathematic model of a SAGSHP system was built and a parametric analysis for Birmingham which is a city located in the UK’s West Midlands was conducted. Two scenarios based on two different dwellings were investigated, the one was a house recently erected and the other was a refurbished house. As regards the new house, simulation results showed that the utilized energy for space heating and Domestic Hot Water (DHW) can vary from 33% up to 73% RES dependent and, at the same time, electricity generation can be 2.21 times higher than the system’s demand. As regards the energy renovated dwelling, the RES contribution to the delivered heat was found to be between the 33% and 63%, while the electricity generation did not result in any surplus energy from the consumed. Finally, by making use of SAGSHP system instead of a natural Gas boiler, the reduction of CO2 emissions was found to be between 300kg/year and 2,170kg/year for the new building and from 245kg/year up to 3,221kg/year for the refurbished house, respectively. In both cases, SAGSHP systems proved to be a feasible practice for greater energy independence from non-renewable energy sources with substantial positive impact on the greenhouse gasses emissions

The production of Wara cheese from locally sourced coagulants and its nutritional evaluation

The use of vegetable extracts as milk coagulants has evolved recently in soft cheese processing. In this study, two types of cheeses were produced from locally sourced raw cow milk using two different coagulants, Calotropis procera leaf and CaCl2. Protein, fat, Zn, Mg, and Fe were the nutrients and minerals that were assayed. The protein (18.4%), Fat (7.93%), Mg (4.13%), Zn (4.01%), Fe (2.59%) of Calotropis procera coagulated cheese was significantly higher than CaCl2 coagulant produced cheese with protein content of (9.13%), Fat (5.53%), Mg (2.34%), Zn (2.59%), Fe (1.13%). The higher ash content in the cheese produced with CaCl2 coagulant makes it susceptible to microbial growth, as a result, reducing its shelf-life. The study suggests that cow milk and Calotropis procera produced cheese appears promising in nutritional contents with further quality improvemen

A comparison of analytical and numerical model predictions of shallow soil temperature variation with experimental measurements

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.In several fields of enquiry such as geothermal energy, geology and agriculture, it is of interest to study the thermal behaviour of shallow soils. For this, several analytical and numerical methodologies have been proposed to analyse the temperature variation of the soil in the short and long term. In this paper, a comparative study of different models (sinusoidal, semi-infinite and finite difference method) is conducted to estimate the shallow soil temperature variation in the short and long term. The models were compared with hourly experimental measured data of soil temperature in Leicester, UK, at depths between 0.75 and 2.75 m. The results show that the sinusoidal model is not appropriate to evaluate the short-term temperature variations, such as hourly or daily fluctuations. Likewise, this model is highly affected by the undisturbed ground temperature and can lead to very high errors. Regarding the semi-infinite model, it is accurate enough to predict the short-term temperature variation. However, it is useless to predict the long-term variation at depths greater than 1 m. The finite difference method (FDM) considering the air temperature as a boundary condition for the soil surface is the most accurate approach for estimating both short and long-term temperature variations while the FDM with heat flux as boundary condition is the least accurate approach due to the uncertainty of the assumed parameters. The ranges of errors for the sinusoidal, semi-infinite and FDM are found to be from 76.09 to 142.13%, 12.11 to 104.88% and 1.82 to 28.14% respectively

The Significance of Scaling Effects in a Solar Absorber Plate with Micro-Channels

The file attached to this record is the authors final peer reviewed version. The publisher's final version can be found by following the DOI link.This paper investigates the significance of some micro scaling effects in micro-channel absorber plates. These plates are to be used in a proposed compact (thin and light-weight) solar thermal flat plate collector (FPC). Forced convection experiments were performed on an instrumented metal plate with micro-channels. Reynolds numbers were in the range 10–100 and fluid inlet temperatures ranged from 5 to 40 °C. Scaling effects such as viscous dissipation and entrance effects had insignificant impact on the measured average Nusselt number. However, conjugate heat transfer and measurement uncertainties were significant. Conjugate heat transfer was found to reduce the Nusselt number which agrees with the literature, this also resulted in a Peclet number dependent Nusselt number. The local Nusselt number was observed to vary axially despite satisfying the criteria for neglecting entrance effects; this variation increased with the Graetz number. It was observed that the position of the thermocouples can result in an under-estimation of the Nusselt number. The results are beneficial for the design and operation of micro-channel absorber plates

Compositional Analysis of Lignocellulosic Materials: Evaluation of an Economically Viable Method Suitable for Woody and Non-woody Biomass

The determination of the composition of lignocellulosic substrate is a crucial step in order to determine the overall efficiency of the processes designed to convert lignocelluloses to ethanol. Standard methods as gravimetric, chromatography, and spectroscopic are routinely explored in the scientific literature. This paper details our investigations in the application of economically viable gravimetric methods particularly suitable for developing countries. The methods were proven to be reproducible and representative for the analysis of biomass as sugarcane bagasse, siam weed, shea tree sawdust

Acid Hydrolysis of Lignocellulosic Content of Sawdust to Fermentable Sugars for Ethanol Production

This study evaluates the yield of glucose from acid hydrolysis of cellulosic content of sawdust, at ambient temperature and atmospheric pressure, and the effect of yeast concentration on its subsequent fermentation to ethanol. The method used involves acid hydrolysis of sawdust, with varying acid molarities of 18M, 15M, 10M, 5M and 1M. The product, consisting mainly of simple sugars, was subsequently fermented with varied concentrations of yeast of 0.5g/20ml, 1g/20ml, 3g/20ml, 5g/20ml and 7g/20ml in order to obtain ethanol. The result obtained shows that there is a gradual increase in the glucose yield with increasing acid molarity from 1M until a critical optimum point is obtained at a high acid concentration of 15M. Beyond the molarity of 15M up to the 18M limit, there exists a decline in the ethanol yield, from the optimum point. The ethanol yield from the fermentation of the resulting fermentable sugars gave the same pattern as the glucose yield irrespective of the yeast concentration used for fermentation. The evaluation of the concentration of yeast on the fermentation of hydrolsed lignocellulosic contents shows that the optimum ethanol yield is obtained at a yeast concentration of 3g/20ml for all the varying acid concentrations. A combination of acid concentration of 15M and yeast concentration of 3g/20ml therefore gives the optimum conditions, at moderate temperature and pressure, for the acid hydrolysis of sawdust’s lignocellulosic content and the fermentation of the resulting product

Heat Transfer in Low Reynolds Number Flows Through Miniaturized Channels.

The use of miniaturized channels as heat sinks/ heat exchangers is of great importance due to advantages of compact size and high heat sinking capabilities. The small hydraulic diameters of these miniaturized channels imply a higher pressure drop and consequently higher pumping power. Therefore, where possible, the pumping power required may be reduced by running applications at low flow velocities. This paper therefore investigates the heat transfer in low Reynolds number flow through miniaturized channels. Forced convection experiments were performed on 2 instrumented metal plates with 0.5 mm and 0.25 mm deep channels respectively. The channels were 2 mm wide and 270 mm long. A propylene glycol-based heat transfer fluid for solar collectors, Tyfocor® LS, was used as the working fluid. Reynolds numbers were in the range 10 – 100 and fluid inlet temperatures ranged from 5 – 60 °C. The measured Nusselt numbers were observed to depend more on the Peclet number and less on the geometry. Peclet number dependent Nusselt numbers was attributed to miniaturization scaling effects. A correlation for estimating the Nusselt number in terms of the Peclet number and hydraulic diameter was proposed. The results are significant in predicting the heat sinking performance in applications having low Reynolds number flows through miniaturized channels such as compact solar thermal collectors

Thermal analysis of a solar collector absorber plate with microchannels

The file attached to this record is th authors final peer reviewed version. The publishers version can be found by following the DOI link below.Experimental and theoretical analyses were carried out to investigate the absorber plate temperature distribution for compact (thin and light-weight) solar thermal collectors. An analytic model combining convective heat transfer with axial conduction in the metal plate was developed. Forced convection experiments were then performed on an instrumented metal plate with micro-channels 0.5 mm × 2 mm × 270 mm long, at various flow rates; the heat transfer fluid was Tyfocor® LS. Reynolds numbers were in the range 10–100 and fluid inlet temperatures ranged from 5 to 60 °C. The predicted plate temperature profiles from the analytic model were in close agreement with the measured profiles. Thermal entry lengths were found to be significant and resulted in slight variations at the entry portion of the plate at higher flow rates. The model was used to study the effects of varying design/operating parameters and showed that axial conduction can significantly alter the temperature profile in the plate