Lawrence Berkeley National Laboratory

Much research has gone into technologies to mitigate urban heat islands by making urban surfaces cooler by increasing their albedos. To be practical, the benefit of the technology must be greater than its cost. This report provides simple methods for quantifying the maxima of some benefits that albedo increases may provide. The method used is an extension of an earlier paper that estimated the maximum possible electrical energy saving achievable in an entire city in a year by a change of albedo of its surfaces. The present report estimates the maximum amounts and monetary savings of avoided CO2 emissions and the decreases in peak power demands. As examples, for several warm cities in California, a 0.2 increase in albedo of pavements is found to reduce CO2 emissions by < 1 kg per m2 per year. At the current price of CO2 reduction in California, the monetary saving is < US$ 0.01 per year per m2 modified. The resulting maximum peak-power reductions are estimated to be < 7% of the base power of the city. The magnitudes of the savings are such that decision-makers should choose carefully which urban heat island mitigation techniques are cost effective.