Performance of Eight Memphis 1000 Solar Water Heaters with External Heat Exchangers for the Period October 1979 to September 1980: Analysis of Monitoring Data

摘要

The performance of eight solar water heating systems in the TVA Memphis 1000 program were monitored with instrumentation that was visually read daily during the period October 1979 to September 1980. The quantities measured and recorded were: (1) solar energy contribution to the water heating; (2) gallons of hot water used; (3) electrical power consumed by the booster tank heater elements; (4) pump run times; and (5) heater element run time. These data were analyzed by computer to produce 4-page monthly reports on each customer. The average yearly customer energy saving was 2676 kWh which was worth $83 at the October 1979 power rate of 0.031 $/kWh and $103 at the September 1980 rate of 0.0385 $/kWh. These savings were 15% less than predicted by the FCHART computer program. The yearly average hot water consumption of 7 customers was 81 gallons per day with a daily per person usage of 21.8 gallons. These usages are somewhat higher than expected and may be due to a delivery temperature lower than 140 exp 0 F which would cause increased consumption. One customer was thought to have a system problem based on a comparison with other customers of pump run times and solar contribution to the water heating. A differential controller problem was strongly suspected. An economic analysis was performed knowing the system performance and economic parameters. A 9-year payback was calculated when defined as the years until fuel cost savings equal the mortgage principal minus the tax credit. The present value of the cumulative solar savings was $783. (ERA citation 08:004723)