| Abstract |
The first of two perennial challenges for efficient cost-effective combined heat and power (CHP) schemes has been the assurance of steady customers throughout the day for both the electricity and heat outputs in order to balance flows and minimize the need for, and capital expense of, thermal energy storage. The other challenge has been to co-locate these consumers in order to minimize the extent of the heating district, hence the capital expense of the transport infrastructure, especially the steam or hot water pipelines. In addition, for geothermal CHP, steady flow is often a necessity on the supply side in order to avoid shutting in production wells, which imposes yet another requirement for either steady flow on the demand side, or expensive storage. Cascading direct users from high-grade to low-grade heat only compounds this problem of synchronization and marshalling, although geoexchange tricks such as asynchronous aquifer thermal energy storage could be useful. Most CHP and direct-use developers focus on factories as users of heat, but factories do not operate around the clock. Because their thermal demands are episodic not steady, many promising candidates for direct-use are rejected at the first stage of economic analysis. We suggest that developers should expand their horizons instead. Herein, the authors present their geothermal Tetrageneration(TM) concept, right-sized for an eco-tourism/hospitality/health care cluster built around the well(s), which would provide sustainable employment, electricity, sanitation and a better life for the host community. Eco-tourism is one of the developing world's most sustainable, low-impact but high-value, rewarding, and promising sectors for economic development in the 21st century. Most of the countries on the Ring of Fire possess these two: unique ecological areas and geothermal resources. The final piece of the puzzle is that geothermal resources of the east African Rift system (EARS) tend to be near or within the world's most famous wildlife parks. Eco-tourists do expect a certain standard of sanitation and accommodation, which means lots of clean hot water, almost around the clock, for bathing, cooking and doing laundry. However, there is another user generally overlooked by developers: community health and sanitation. Community clinics also need lots of clean hot water, almost around the clock, for sterilizing, bathing, cooking and laundry. A convenient mnemonic for this pairing might be "hospitality and hospitals". With proper design, each thermodynamic use can be efficiently cascaded, from higher-order forms such as live steam and electricity, to lower-order uses down the chain of benefit, before the primary geofluid is injected back into the reservoir, thus assuring its long-term health too. It goes without saying that modularizing such a system to fit into standard twenty-foot-equivalent-unit (TEU) form factor makes it transportable anywhere on earth, and extensible as well. One of the authors conceived one such quadruple system for Tetra Tech that is called Tetrageneration(TM). |