SAN ANTONIO – As another hot summer approaches, KSAT Explains went to a CPS Energy solar facility for a Q&A about how energy generated by the sun works.

KSAT spoke with Mike Hale, CPS Energy’s Interim Senior Director of Market Operations, at the utility’s solar facility near State Highway 151 on property owned by Southwest Research Institute.

KSAT: How many solar facilities does CPS Energy have?

Hale: Eighteen different facilities. So, there are many in the San Antonio area, but then we also have larger solar facilities that are located south towards Corpus (Christi) and as far as north around the Abilene area.

CPS said sixteen of those sites are currently up and running. Two more facilities will be coming online in the next few years. KSAT: How is the power generated here used?

Hale: The way power works is (that) it gets consumed close to where (the) load is. Businesses and companies that are local to that will consume that power first, and any excess will continue to transmit through our transmission lines onto the grid and get consumed at the next point where load is needed.

According to Hale, this means local customers get the first priority and what’s left goes onto the statewide power grid operated by ERCOT.

KSAT: What percentage of all the generation sources that CPS has is solar?

Hale: We have roughly about 10,000 megawatts of generation capacity in our portfolio. Solar is about 1,000 or so megawatts right now. So, on average, about 10% to 15%.

Hale said one megawatt of generation powers 250 homes per hour.

KSAT: When we have a whole lot of clouds, is energy still being created out here?

Hale: It is. So, the solar panels actually will still work when it’s cloudy. It works on the theory of solar radiation. So, those panels are really taking the energy from the sun, the radiation from the sun and converting that into usable electricity.

KSAT: Can you explain how these panels work?

Hale: They have automatic trackers that will actually track the position of the sun in the sky. You get energy of electrons moving around as that solar energy hits the materials in the panel, generally silicone. It actually causes that reaction of electrons to be moving around, and there’s certain equipment in those panels to direct the flow of those electrons, which creates current flow.

Hale said the inverters convert that flow into an alternating current, which is what’s used to power homes and businesses.

KSAT: What is the relationship between a facility like this and somebody who, at their own home, has solar panels on their roof?

Hale: If they’re running their air conditioner, their appliances, and they have rooftop solar on their house, that generation is really netting out with the consumption, and they’re really not selling to the grid, if you will. But they’re producing or offsetting a portion of the needs that their house needs.

Instead of tapping into the CPS Energy source, Hale said homeowners with solar panels use that to power their home until that source runs out. Then, they tap into the same CPS source other customers use.

KSAT: How is energy created by these panels stored and used later?

Hale: During the middle part of the day, when the sun is shining the most, you can actually use energy storage to charge your batteries with that cheap source of solar power. And when the solar ramps out at night, you actually discharge your batteries, which is using that same energy that the solar helped provide.

Hale said solar batteries are filled and tapped into daily.

KSAT: There’s only so much storage in there. Is there any generation that is lost?

Hale: In those periods of time where you have an abundance of energy being produced by solar or wind, what you can do is actually back down other resources so you may not have to use as much of gas generation or coal generation.

KSAT: Who’s paying for it? Is it ERCOT that pays CPS Energy for what you all generate?

Hale: We’re going to get a bill from ERCOT for all the load that we consume as a utility. At the same point, the energy that we sell off our generation, we’re gonna get a payment from ERCOT. ERCOT is the clearinghouse for the market, and so, we’re really getting both sides. We’re getting charged for the load. We’re being paid for the generation.

Hale said the net amount is passed on to customers.

Solar power generation is growing for CPS Energy, but it is still roughly a quarter of the power supply needed statewide.

Hale: That means our fossil fuel, our coal, our nuclear, our gas generation, our wind, and our energy storage — all of that is needed to go through these very high demand periods of the season.

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