Pacific Gas and Electric Company - Emerging Technologies ...

Evaluation of the Freus Residential Evaporative Condenser System in PG&E Service Territory
Data, in comma-delimited ASCII format, was downloaded daily to a central computer and
screened using software to review data quality. Out-of-range data was noted and further
investigated visually to determine whether a sensor or monitoring error exists or equipment has
failed. Data review was performed using an EXCEL spreadsheet that allows for loading and
graphing of all key monitoring parameters in a weekly time series format. Weekly performance
reports were developed for each site and emailed to the PG&E project manager. The reports
included plots of temperature, relative humidity, unit power, water consumption, effectiveness,
and EER. A sample report is included in Appendix B.
Sensible cooling delivered by the evaporative condenser was determined on a 15 second interval
as shown in Equation 1. Total cooling (sensible plus latent) was also calculated based on the
change in air enthalpy 8 between the return airstream measurement and the supply air
measurement (see Appendix B). Historically these enthalpy measurements have not always
produced reasonable results due to sensor accuracy limits and the inherent variations in
temperature and humidity that occur downstream of an evaporator coil. In this project we
focused on the sensible cooling measurement as the key performance descriptor. For dry
California climates, the impact of ignoring latent is typically small (