Effective Energy Metering of Solar Domestic Hot Water Systems for Inclusion in Green Power and Renewable Portfolio Standards

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Title: Effective Energy Metering of Solar Domestic Hot Water Systems for Inclusion in Green Power and Renewable Portfolio Standards
Author: Cleveland, Thomas Hilburn
Advisors: Dr. Richard Johnson, Committee Chair
Abstract: The goal of this metering experiment was to construct and validate a methodology to meter accurately, reliably, and affordably the amount of electrical energy offset by the collection of solar thermal energy in a solar domestic hot water (SDHW) system. Currently there are thermal energy meters on the market, but no generally accepted method for metering the thermal energy gain supplied by solar thermal collectors. An experimentally proven metering methodology that instills confidence in both consumers and policy makers would help open the door for the participation of domestic solar thermal energy in state or national Green Power and Renewable Portfolio Standards (RPS) programs. SDHW inclusion in such programs could significantly increase its use. The experimental setup was a thermocouple-monitored three-meter metering system installed on a SDHW system in the NC Solar House. An electric energy meter recorded the energy supplied to the tank via the electric heating elements. The other two meters were thermal energy meters. One was positioned on the solar loop to measure solar energy collection. The other was attached across the water heater to measure the useful thermal energy in the hot water delivered to the house. Three separate months of data were collected, and extensive heat transfer analysis was carried out to model the system thermal losses. Then a TRNSYS model of the system was validated with the recorded data. TRNSYS simulations indicated that the hot water load, as measured with a thermal meter, minus the electric energy input, as measured by an electric meter, plus the amount of energy lost by the tank (based on a standard experimental daily loss) is equal to the daily amount of energy offset by the use of the solar system. Even with extreme hot water draw profiles, this methodology worked exceptionally well for metering the amount of electric energy offset by the solar energy gain.
Date: 2004-04-19
Degree: MS
Discipline: Mechanical Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/1152

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