Research in Energy and the Environment

Several important problems face us in transitioning to a more sustainable energy system. One set of problems relates to the environmental impacts created by the current approach, which relies heavily on fossil fuels -- these range across scales from local to regional effects caused by particulate, sulfur and nitrogen oxide emissions from combustion to global concerns over carbon dioxide. Another important aspect is the maldistribution and depletion of fossil resources (oil, natural gas, and coal). All of this suggests that we should diversify our energy supply options while we seek to minimize the environmental effects associated with fossil fuel use. So far, progress has been slow, in part because the technologies associated with renewable energy capture and recovery cannot compete economically with today's low-cost fossil fuels. Much of the research in our group focuses on these problems. For example, investigations are aimed at producing cleaner fuels and renewable biomass and geothermal energy systems, and ohters are focused on processes to remediate environmentally contaminated areas.

Professor Tester's research group has been developing a range of experimental and theoretical methods to probe kinetics, phase behavior and transport phenomena in compressed and supercritical media. For example, measurements of reaction rates and product distributions have successfully been linked to ab initio quantum chemical calculations to quantify the effectiveness of reforming and oxidation processes in supercritical water to detoxify chemical and military wastes. Improved fundamental understanding of the role of supercritical water, both as a solvent and as a reactant, has been obtained for a number of model wastes ranging from methylene chloride to methyl tert-butyl ether (MTBE) to methyl phosphoric acid (MPA).

Synthetic pathways are also being pursued using mixtures of compressed and supercritical fluids in a collaborative program with Professor Rick Danheiser in Chemistry and Professor Andrew Holmes at Cambridge University, UK. The key idea involves a green chemistry approach where environmentally benign solvents such as water and carbon dioxide are used as the media to carry out selective carbon-carbon and carbon-nitrogen bond forming cyclo-addition reactions for producing pharmaceutical intermediates and specialty chemicals. So far, we have been successful in demonstrating the use of power ultra sound to produce emulsified bi-phasic mixtures of near-critical carbon dioxide and water that enhance reaction rates between model Diels-Alder reactants.

The third area under investigation is the development of a new approach to drilling ultra deep holes in the earth using thermal spallation and fusion rather than the conventional cutting and grinding approach.

Earlier work in our group has quantitatively characterized rock spallation phenomena using supersonic combustion flame jets at low pressures and fluid densities in shallow hole drilling to show that they will penetrate very hard rock at about 5 to 10 times the rate of conventional bits with little or no wear. Ultra deep drilling to 10+ km will require having an intense heat source at high pressures of 1 kbar or more. Building on our experience operating in high-pressure, supercritical water environments, we are analyzing the feasibility of using hydrothermal flames as a heat source to spall and melt rock in confined bore holes. Using conventional drilling technology, an exponential dependence of drilling cost on well depth results in part from the inherent wear to drilling equipment and the need for drill bit replacements.

If the thermal method works, we are optimistic that the current exponential dependence would be replaced with a linear dependence of cost on depth. Such technology would drastically improve the economics of geothermal energy recovery from very deep reservoirs, thus making heat mining from the deep earth a universally accessible energy source.