Optimal financial choices for the insulation of buildings

A method for determining the economic priorities with which various thermal insulation options should be adopted for domestic purposes is described and some results presented.

Climate warming could shift the timing of seed germination in alpine plants

Background and AimsDespite the considerable number of studies on the impacts of climate change on alpine plants, there have been few attempts to investigate its effect on regeneration. Recruitment from seeds is a key event in the life-history of plants, affecting their spread and evolution and seasonal changes in climate will inevitably affect recruitment success. Here, an investigation was made of how climate change will affect the timing and the level of germination in eight alpine species of the glacier foreland. MethodsUsing a novel approach which considered the altitudinal variation of temperature as a surrogate for future climate scenarios, seeds were exposed to 12 different cycles of simulated seasonal temperatures in the laboratory, derived from measurements at the soil surface at the study site.Key ResultsUnder present climatic conditions, germination occurred in spring, in all but one species, after seeds had experienced autumn and winter seasons. However, autumn warming resulted in a significant increase in germination in all but two species. In contrast, seed germination was less sensitive to changes in spring and/or winter temperatures, which affected only three species.ConclusionsClimate warming will lead to a shift from spring to autumn emergence but the extent of this change across species will be driven by seed dormancy status. Ungerminated seeds at the end of autumn will be exposed to shorter winter seasons and lower spring temperatures in a future, warmer climate, but these changes will only have a minor impact on germination. The extent to which climate change will be detrimental to regeneration from seed is less likely to be due to a significant negative effect on germination per se, but rather to seedling emergence in seasons that the species are not adapted to experience. Emergence in autumn could have major implications for species currently adapted to emerge in spring

Future prospects for the electric heat-pump

Trials are underway to investigate the technical and economic feasibilities of air-source heat-pumps in the UK. These trials show that the use of heat-pumps for domestic heating has significant potential environmental benefits in terms of the reduction of carbon dioxide emissions as long as the performance of current models can be improved. Indications are that, with the use of existing technology, running costs are potentially competitive with existing means for residential space-and-water heating. Considerable potential exists to raise the seasonal coefficient-of-performance of domestic heat-pumps to above 3. Combining performance improvements, a preferential heat-pump energy-supply tariff and possibly a government subsidy to help meet the capital cost could make domestic heat-pumps economically and environmentally competitive with the latest condensing-gas boilers. Some alternative designs for heat pumps are reviewed and assessed. This survey discusses basic principles and economics as well as the current and possible future developments in the design of domestic heat-pumps. It is concerned primarily with electric heat-pumps used in the UK for domestic purposes: these provide energy for whole-house heating and/or domestic hot-water.

Modelling the role of algae in rice crop nutrition and soil organic carbon maintenance

Photosynthetic aquatic biomass (PAB – algae and other floodwater flora) is a significant source of organic carbon (C) in rice-based cropping systems. A portion of PAB is capable of fixing nitrogen (N), and is hence also a source of N for crop nutrition. To account for this phenomenon in long term simulation studies of rice-based cropping systems, the APSIM modelling framework was modified to include new descriptions of biological and chemical processes responsible for loss and gain of C and N in rice floodwater. We used well-tested algorithms from CERES-Rice, together with new conceptualizations for algal dynamics, in modelling the contribution of PAB to maintenance of soil organic C and soil N-supplying capacity in rice-based cropping systems. We demonstrate how our new conceptualization of PAB growth, turnover, and soil incorporation in flooded rice systems facilitates successful simulation of long-term soil fertility trials, such as the IRRI Long Term Continuous Cropping Experiment (35+ years), from the perspectives of both soil organic carbon levels and yield maintenance. Previous models have been unable to account for the observed maintenance of soil organic C in these systems, primarily due to ignoring inputs from PAB as a source of C. The performance of long-term rice cropping system simulations, with and without inclusion of these inputs, is shown to be radically different. Details of our modifications to APSIM are presented, together with evidence that the model is now a useful tool to investigate sustainability issues associated with management change in rice-based cropping systems

Thermally stratified hot water storage systems

Thermal stratification in sensible thermal energy storage systems using water has been studied experimentally. Design correlations, suitable for use with cubical storage tanks, have been derived. Analytical predictions of the transient development of the thermocline are compared with experimental measurements and show good agreement. Linear systems theory is found to be a valid and accurate method of simulating the dynamic performance of stratified thermal energy storage systems if the rate of heat loss from the store is minimised.