Characteristics of DE Technologies

Technology	Benefits	Drawbacks	Fuel Choice	Size (kW)
Fuel Cells High temp: Installed cost is highly variable; efficiency is 45% to 55% Low temp: Installed cost is $2,000 to $3,000/kW; efficiency is 30% to 40%	Very high fuel efficiencies from hydrogen to electricity Potential to operate baseload with utility standby Possible residential application — a no-moving-parts energy appliance Very high efficiencies when combined with heat recovery Green technology — water and heat are only emissions from hydrogen fuel, low emissions from other fuels	Few commercially available devices Most research efforts are for automotive applications Need for fuel reformer in almost all applications (reduced fuel to electrical efficiencies) Not a zero-emission technology — the effect of that may vary by state Cold start is 1-2 days for MCFC, 3 hours for PAFC, 1 hour for PEMFC, and 2 minutes for SOFC	Direct by hydrogen; natural gas, propane, methanol, or other hydrogen-rich source through reformer	MCFC (molten carbonate fuel cells): 250-2,850 PAFC (Phosphoric acid fuel cells): 200 PEMFC (proton exchange membrane fuel cells): 3-250 SOFC (solid oxide fuel cells): 225-2,240
Photovoltaic Installed cost is highly variable	No variable costs for fuel No moving parts — inexpensive maintenance and long life No emissions, no noise Can be used for peak shaving Highly reliable, mature technology	Big foot print (600 ft²/kW) High installed costs Not suited for baseload Not suited for standby except when accompanied by storage Variable energy output	None	Limited by available area
Large Wind Turbines Installed cost is highly variable	No variable costs for fuel In utility implementation, zero emissions may allow green power price premium Mature technology Multiple manufacturers	Need to meet siting requirements Generation is intermittent with wind, and energy output can vary with wind speed squared or cubed over operation range. Not appropriate as backup or off-grid applications Needs utility source for energy purchases and sales Can require footprint up to 100ft²/kW	None — need winds of >12 mph or sometimes higher	<1-1,000
Internal Combustion Installed cost is $400/kW to $600/kW; efficiency is 28% to 37%	Bulk power delivered when utility is unavailable Fast startup allows less sensitive processes to be served without need for UPSs (emergency lighting, HVAC, elevators, some manufacturing processes) Very mature, stable technology Can be paralleled to grid or other generators with controls package Can be very efficient when combined with heat recovery	Insurance policy effect: Capital is only being used when standby generator is running Marginal cost of production generally favors utility source in all but rare occasions Environmental issues — emissions and noise Possible on-site fuel storage needs	Diesel, natural gas, propane, bio-gas, other petroleum distillates	<1-6,000
Small Gas Turbines Installed cost is +/- $650; efficiency is 25% to 40%	Highly efficient when used with thermal recovery Technology commercially available today — most likely candidate for on-site needs >3MWe in DG application Can operate baseload, standby, or peaking Several manufacturers Relatively low installed costs	Potentially onerous siting and permitting requirements Environmental issues — emissions and noise Possible on-site fuel storage needs	Natural gas, distillate, methane	3,000-15,000
Microturbines Installed cost is $750/kW to $900/kW; efficiency is 28% to 33%	Thermal recovery improves efficiency Thermal output for residential or small commercial apps Operable as base, peaking, or standby Commercially available in limited quantities	Insufficient thermal output for industrial apps	Natural gas, propane, diesel, multi-fuel	15-250

Source: Andersen
Reprinted with permission from Public Utility Reports, Inc., from the Summer 2001 issue of Fortnightly's Energy Customer Management. No article may be reproduced in any form or by any method, in whole or in part, without the written permission of the publisher.

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