LETTER: Large solar projects have costs

I mostly agree with Wayne Willis (“It’s hot,” Saturday letter to the Review-Journal), but would clarify a few points.

First, I’m all for building photovoltaic plants. Just be careful where you build them, as they are heat islands. Effectively, it’s like putting black asphalt on the same area. In Las Vegas proper, that area is trivial compared to the paved roads and dark roofs. But for Boulder City, and the nearby PV array, it’s probably not trivial.

I put solar panels on my roof in 2015 when the prevailing view was that the heating effect was very small. Then in 2016 the prestigious journal Nature published “The Photovoltaic Heat Island Effect: Larger solar power plants increase local temperatures.” Planners should think twice about where they site large PV arrays.

Second, as for efficient AC units and heat pumps: The vast number of AC units in Vegas are refrigerated air. They are technically heat pumps run “backwards.” Their efficiency is mainly determined by the second law of thermodynamics. My AC unit can actually be run as a heater or cooler, depending on where it pulls heat (inside or outside the house). The catch is that many heat pump/AC units, just a few years old, use a refrigerant that is actually worse for the environment than a gas heater, given that they invariably leak a very potent greenhouse gas.

The refrigerants are getting more and more greenhouse-friendly, but the best refrigerants aren’t even legal in the United States yet. However, it is still legal to sell heat pump units based on the older refrigerants, and I’m sure some vendors want to sell them at reduced prices. Evaporative coolers are more efficient than refrigerated air, but rarely reach a temperature change of more than 25 degrees F from the outside.