Greenbuilding Archive for April 2001

Ted: Have I offended you too in another life? I don't recall, so please explain why you failed to correct the clear ignorance of standard engineering terms displayed by John Herbert, John D'Angelo & Malcolm. I seemed to have incurred their rath for merely quoting from various reports; including the DOE evaluation of GFX that assumed "100%" Conversion Efficiency (CE) in the "Table 1" inserted below. Maybe Milton Pravda, an NBS (now NIST) Grant evaluator rounded off 99.5% to 100%.

The report by Old Dominion U. summarized @ www.oikos.com/gfx/tests.html actually measured the Energy Factor (EF) of several "green-bundles" and reported the EF range of a tankless water heater as 0.98 to 1.0. They used standard experimental procedures and may have rounded off a meter reading of 99.5%, for all I know. Call them to complain for not quoting 0.99999999 +/- ????.

Would you have me misquote these reports?

Also, the definition of CE is (Hot-Water-Power-Out/Site-Power-In). The denominator does not include "source" power at either a power plant, gas well, oil well, or the Sun! Similarly, the definition of EF for a water heater is (Hot-Water-Energy-Out/Site-Energy-In) over a specific time period with a given hot-water draw schedule.

If you take issue when one rounds off a measurement to 100%, will you become aghast when the standard measurement of EF exceeds unity if applied to heat pump water heater (HPWH) and DHR systems?

Like-it-or-not, standard definitions for EF & CE can both exceed unity (100%) if either a HPWH or GFX is bundled with a tank-type electric water heater. Domestic HPWH's like Hot Shot or Environmaster cannot be bundled with tankless water heaters. Consequently, standing loss causes the water heater EF to fall below the heat pump's C.O.P. That's why the Old Dominion report shows an EF range between 1.7 & 1.9 for a GFX-Tankless Bundle compared 1.33 & 1.57 for a HPWH/Tank-Type Bundle.

TABLE 1
SIMPLE PAYBACK SUMMARY FOR REDESIGNED THIN-FILM HEAT EXCHANGER
Source: DOE Grant Evaluation of GFX Recommendation No. 382, OERI No. 009925 Dec. 1986

Energy Source	Conversion Efficiency	Energy Cost	Dollar Savings per Year	Simple Payback in Years (Without Interest)
Electrical	100%	8.66�.kWh	103.49	2.09
Natural Gas	76%	$6.35/106 Btu	34.09	6.34
Oil	55%	$1.00/gallon	53.48	4.04

Notes: 1. Energy saving for an average household is 1195 Kw-hr thermal per year.
2. Installed cost of heat exchanger is $216. [New Construction]
(Table entries are based on Pravda's 53% design. Today's version, Doucette's Model G3-60 offers over 60% efficiency)

Are we having fun yet?

Carmine

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WaterFilm Energy Inc.; P.O. Box 128; Medford, NY 11763
Voice: 631-758-6271 [Fax: 631-758-0438]
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