Solar PV and geothermal in interesting hybrid plant set-up by Ormat in Nevada
To cover the parasitic load and push up produced electricity, Ormat Technologies plans for an 18 MW Solar PV plant next to its 24 MW Tungsten geothermal power plant in Nevada/ U.S.
We recently reported on the planned set up of a solar PV plant next to a geothermal power plant by Ormat Technologies in Nevada.
CleanTechnica goes a bit deeper in its reporting on the planned project, providing some details on the hybrid-nature of the set up. The 24 MW Tungsten geothermal power plant started commercial operation in December 2017, as we then reported.
The planned 18 MW solar PV plant is expected to generate an average of around $15 million annual revenue. The buyer of the electricity is Southern California Public Power Authority (SCPPA) at a price of $75.5 per MWh, or around $0.075/ kWh.
The plan is for the solar plant to supply power for the parasitic load required to operate the geothermal plant. So why is electricity needed to operate the plant?
Parasitic load essentially is the electricity consumption of the plant, e.g. for pumps and other elements that require electricity to operate the plant. Generally geothermal plants use their own electricity production to cover the parasitic load, which is normally in the range of 2-5%, but can reach significantly more for some binary plants. (source)
As described in the article, the geothermal plant does not operate as efficiently at high mid-day temperates, as it is hotter and the cooling towers are not as efficient, effectively decreasing the output of the plant.
Geothermal power plants require cooling in order to condense the vapour that feeds the turbine, lowers the heat rejection temperature, raises power output and increases the heat to power conversion efficiency. The electricity output of these plants deteriorates in the summer period. The reason is that plant efficiency depends directly on the geothermal resource and the ambient temperature.
With the solar PV, the overall energy output is boosted maximizing the energy sold to SCPPA. There are other cases of solar-geothermal solutions, where thermal solar cooling lines are set up to lower the temperature of the solar PV, helping it to maintain maximum efficiency.
Supposedly, the PV solar cells are losing efficiency rapidly when the temperature of the panels goes above 149 degrees Fahrenheit (or 65 centigrades).
In its filings for 2017, Ormat announced a focus in installing solar PV systems in some of [its] geothermal power plants to reduce internal consumption loads. … while also looking for hybrid projects involving intermittent power and energy storage”.
Clearly an interesting technology play that could see further application elsewhere.