Environmental Impacts of Utility-Scale Solar Energy

 

by Jincy Varughese

With utility-scale solar energy (USSE) systems growing in number internationally, many have researched the environmental impacts of such systems. Hernandez et al. (2014) reviews studies examining the environmental impacts of USSE on biodiversity, water, human health, and potential solutions to mitigate impact. Continue reading

Cooling Buildings by Radiating Heat to Outer Space

by Emil Morhardt

Global warming is occurring because there is a slight imbalance in the amount of sunlight striking the earth over the amount of heat being lost. The only way the earth can shed heat is by radiating it into space, and the problem is that with the current concentrations of greenhouse gases in the atmosphere, earth isn’t quite warm enough to radiate enough heat outward to stabilize the temperature. One way to address this imbalance, often considered in proposals for geoengineering, would be to decrease the amount of sunlight captured by the earth, say, for example, by reflecting some of it back into space so it doesn’t have a chance to be absorbed. Another way would be to increase the effectiveness of radiating heat into space, but I haven’t seen any proposals for the latter. Stanford University researchers, however, have just figured out how to accomplish both substantial reflection (97%) of solar radiation and an increase in radiation of heat to space in a single device, such that it can passively cool the air in it by at least 5°C (9°F), and theoretically by almost 20°C (36°F) if protected from convective warming (from the wind or breezes). Their prototype ejects about 40 Watts per square meter, which they figure could be improved to 100 Watts per square meter. This occurs in full sunlight with no energy expenditure whatever, and is the first time a device such as this has been implemented. It won’t solve the global warming problem directly, but once commercialized, it could go a long way toward decreasing the electricity consumption of buildings, much of which is needed only for cooling. Continue reading

Membrane-Free Lithium/Polysulfide Semi-Liquid Battery for Large-Scale Energy Storage

by Allison Kerley

Yang et al. (2013) discussed their new proof-of-concept lithium/polysulfide semi-liquid battery as a potential solution to large-scale energy storage. The lithium/polysulfide (Li/PS) battery uses a simplified version flow battery system, with one pump system instead of the traditional two. The Li/PS battery was found to have a higher energy density than traditional redox flow batteries, with the 5 M polysulfide solution catholyte cell reaching an energy density of 149 W h L–1 (133 W h kg –1), about five times that of traditional vanadium redox battery. The Li/PS battery cells were also found to have a high coulomb efficiency peak around 99% before stabilizing at around 95%, even after 500 cycles. The authors conclude that the Li/PS cells maintain a steady rate of performance after 2000 cycles, and Continue reading

Electricity From Low-Level Heat

by Emil Morhardt

Low-level heat—temperatures 100­–200°C above ambient, the temperature range of a kitchen oven more-or-less—are abundant in the exhausts of all sorts of industrial processes from drying biomass to operating internal combustion engines. They are also much more common in geothermal fields than the higher temperatures needed for traditional geothermal steam power generation, although low-level heat can be used to vaporize high-volatility organic compounds such as propane, which can then power a turbine much as steam would. For the most part, though, this heat is wasted, just released into the environment; but it needn’t be. Researchers at the China University of Geosciences in Beijing and at Stanford University experimented with an array of commercially available thermoelectric power generators (TEGs) Continue reading