On April 26, a delegation of E2 members attended the White House Forum on Energy Security hosted by Deputy Secretary of Defense Bill Lynn and Deputy Secretary of Energy Daniel Poneman. This session pointed out the high costs to the military of its fuel and energy dependence, and focused on several advanced technologies now under development and testing. The commentary below from E2 Member David Willson, proposes that there are also a number of entirely proven practical approaches that might quickly reduce power generation requirements.
| ||E2 Member David Willson (New York).|
David Willson is an E2 member currently living in New York City (New York Chapter). He has more than 25 years of experience in the energy field including consulting, project development, and financing. He has recently developed a resourceful array of potential energy sources for the US military in Afghanistan. You can reach him via email at firstname.lastname@example.org.The Challenge
The Defense Advanced Research Projects Agency estimates that 70 percent of the fuel transported over hazardous supply routes to Afghanistan is used for power generation at base camp and forward operating bases. The delivered cost of JP-8 fuel (standard military fuel for jets, tanks, heaters, etc.) transported by convoy to a large base is estimated at $30-50/gallon. Assuming a modern diesel plan consumes 0.07-0.11 gallons of fuel per kilowatt hour, this implies a generating cost of $3-5/kwh of electrical power. (The cost at forward operating bases, to which fuel is air-lifted, may be up to 10x higher.) Compared to these costs, almost every form of renewable energy is economical, and the military is actively assessing alternatives. Heating, ventilating, and air conditioning (HVAC) needs consume an estimated 65% of the fuel transported in theater. The balance of this note focuses on ways to reduce the demand for energy in Afghanistan, using proven technologies alone or in conjunction with renewables. While this article is focused on Afghanistan, the approaches outlined below may be of relevance to other parts of the world.
Increasing Energy Efficiency
| ||This table illustrates how the various alternatives outlined in this article can be combined to reduce energy consumption, cut costs, and save lives. Click image to enlarge.|
With daytime temperatures of up to 120 degrees Fahrenheit, and wide daily temperature fluctuations (reaching 30-40 degrees in some areas), Afghanistan presents an HVAC challenge. However, it may be feasible to reduce HVAC energy requirements by 90% or more through a resourceful combination of more efficient heating and cooling systems and thermally efficient buildings. Incremental benefits can also be derived by utilizing combined heat and power technology to reduce residual electrical demand. More efficient heating and cooling systems: Geothermal heat pump
technology is well-developed and can be used for cooling tents and buildings, as the temperature is a relatively steady 53 degrees throughout the year just 30 feet beneath the ground. Relatively shallow wells (or trenches) can be drilled adjacent to tents or other structures, permitting a fluid, such as brine, to circulate continuously in a loop from underground to the surface. Circulation can be operated by an electric pump or windmill. While this technology is not yet fully cost-competitive with conventional air-conditioning powered by cheap electricity in the US, the payback period in theater would be a matter of months. Evaporative Cooling
is an old and proven technology that works well where there is low humidity (as in the drier parts of Afghanistan) and a supply of water. The technology requires a breeze, either natural (via a wind scoop) or from a fan; when a fan is used in a desert area, the energy requirement is often less than 20% of a conventional air conditioner. Water can be sourced from non-potable well water or condensed from JP-8 fuel combustion. In areas of the US Southwest similar in climate to areas of Afghanistan, energy savings of more than 85% have been realized even for well-insulated structures. Primitive coolers were embodied in Moghul architecture (such as Delhi’s Red Fort); for modern versions the fan can be solar-powered. Thermally-Efficient buildings:
Heat loss is a major source of energy inefficiency in Afghanistan, given the daily temperature extremes and differential between desired and ambient temperatures. (Heat loss is proportional to the cube of the differential.) This suggests that proper insulation of tents alone might reduce energy consumption substantially. Indeed, the military has experimented with pre-fabricated structural insulated panels that are strong, energy-efficient and cost-effective, and may realize energy savings of 70%.
A more ‘innovative’ approach for larger military bases is an old one: thick-walled adobe, or concrete-type buildings, which embody passive solar heating and cooling. The rule of thumb for adobe structures is that the diurnal maximum and minimum temperatures can be approximately averaged throughout the day by operation of latent heat transfers. During the more humid night, the adobe attracts moisture, which condenses and warms the structure; as the adobe is heated by the sun during the day, the latent heat of evaporation of the resident moisture cools the structure. This latent heat transfer is augmented by thermal transfers, which occur in desert zones such as Afghanistan where the diurnal temperature range exceeds 30 degrees Fahrenheit in the summer. Domed adobe structures have withstood earthquakes (notably, the 1978 Tabas earthquake in central Iran, where some of the few surviving structures were ancient domes). Such domes, as a single fused structure (like an inverted clay bowl), reportedly float over the seismic waves. Moreover, if a higher clay content is used, such structures can be fired to form a hard ceramic material of stone-like strength that has also been proven in its ability to withstand earthquakes. The fuel required for firing is just two barrels of JP-8 fuel, less than one week’s consumption by a single soldier.
Approximately 50% of the world’s population lives or works in earth-made construction. US leadership in perfecting robust and thermally efficient buildings of earthen materials could have a significant long-term GHG reduction benefit, in addition to reducing deforestation attributable to timber use in building. Valuable resources on the topic include CalEarth (www.CalEarth.org
, and near Kabul, the Clay Building Research Centre (www.darah-afghanistan.net
). Combined Heat and Power (CHP):
For larger bases, residual electrical (and hence fuel) demand can be significantly reduced by a centralized JP-8 fuelled skid-mounted mobile turbine with CHP applications. While the electrical efficiency of an open cycle turbine may be only 28%, most of the energy from combustion is in the form of heat which can be used for District Heating & Cooling. The addition of a turbine chiller to take advantage of the turbine exhaust heat significantly increases the total efficiency. Many US campuses have adopted this proven “Trigeneration” approach, whereby power, heating, and cooling are efficiently co-generated. This is a standard and entirely proven approach, which has been demonstrated in thousands of installations worldwide.
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