The city of Cortez has installed enough solar panels on the roof of City Hall to annually produce as much energy as the facility consumes. Shaw Solar, a solar contracting company based in Durango, completed installation of 326 solar panels on Oct. 11, bringing city hall’s solar production peak capacity up to 102 kilowatts.
The city originally installed 14 kW in solar panels on the roof of City Hall in 2016 as it attempted to meet criteria for certification from the Leadership in Energy and Environmental Design program. LEED is a popular building certification that recognizes environmentally responsible construction.
After gathering about two years’ worth of utilities data at City Hall, the city staff was able to provide an estimate of expected annual energy consumption, and therefore how many solar panels would be required to completely offset this consumption.
Using this utilities data, and based on calculations done by an online tool provided by the U.S. Department of Energy, the city of Cortez determined that it needed an additional 88 kW of solar production to become 100 percent solar powered.
Daily energy debtBecause energy production and consumption varies from day to day and month to month, many businesses and governments consider solar energy production on an annual basis. Those measurements tend to be less volatile than other, more frequent measurements and averages.
Solar panels do not always produce energy at the rate that consumers use energy. For example, solar panels produce almost no energy at night, but many appliances and other systems require energy at all times.
This energy “debt” can be offset when solar production outpaces consumption, feeding the electrical grid and other customers with the extra energy generated by the solar array. This happens when sunlight is strong or fair weather precludes the use of climate control systems that consume lots of energy.
Monthly energy debtIn addition to the effects of daylight, solar panels generate less energy on sunny days during winter compared with summer. This happens for some of the same reasons that average daily temperatures are lower during the winter.
In Colorado and other locations far from the Earth’s equator, sunlight strikes the Earth at a more shallow angle during winter compared with summer. This means less light reaches the Earth’s surface to generate ground heat and feed solar panels.
While solar power generation declines in winter, energy consumption tends to climb as residences and businesses engage heating systems to control indoor climates. However, this energy “debt” as well is made up during warmer months, when energy consumption can dip and solar energy generation increases.
Associated costsIn 2005, Colorado adopted rules that allow entities to offset their annual energy costs, and in some cases profit, if their property generates energy for its local power grid via renewable means.
The rules are part of the net metering program, which enables producers of solar energy to gain energy credits in high-production months that can cover their expenses during low-production months.
Mike Ellis, who is in charge of business operations and finance for Shaw Energy, estimates the city may save $200,000 to $400,000 over 25 years thanks to the new panels.
The city will lease the panels from Shaw Energy for six years, at which time ownership of the panels will transfer completely to the city.
