The Effects of Clouds on Solar (via NREL)

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The National Renewable Energy Laboratory, or NREL, recently published extensive data on the effect of cloud cover on solar power installations.

NREL is one of ten national laboratories overseen and primarily funded by the U.S. Department of Energy’s (DOE’s) Office of Science, and is the only federal laboratory fully vested in the research, development, commercialization and deployment of renewable energy and energy efficiency technologies.

The NREL dataset was collected at one-second intervals over an entire year from 17 solar monitors set up on the island of Oahu, near Hawaii’s Honolulu International Airport, and is an invaluable resource to those developing utility-scale solar photovoltaic (PV) systems because it will help them anticipate “weak spots” in solar energy production.

Solar PV energy is one of the cleanest forms of renewable energy. Thanks to falling module prices, it is also one of the cheapest, with module prices from some manufacturers selling for $1 per watt. Unfortunately, it is also intermittent, as when cloud cover for example prevents the full force of the sun’s light from reaching earth, or at night. In fact, solar panel output reacts very rapidly to changes in the intensity of sunlight.

Scientists can do nothing about nightfall, of course, but this newest dataset enables solar system developers to plan for the energy intermittency that results from clouds, and enables electricity grid system managers and planners to develop modalities to prevent this intermittency from crippling the system.

In fact, it is hoped that solar planners can analyze the particular characteristics of cloud shadows, and then reliably model, or predict output from, their individual systems over the long-term.

One not-so surprising discovery was that larger systems tend to exhibit a “smoothing” of energy output, and the causes of that, if examined in detail, might enable solar designers to align their panels or connect them in such a way as to further mitigate cloud cover effects.  The data can be used to model solar PV systems up to 30 megawatts in size.

Called the Oahu Solar Energy Study, the work is a collaborative effort of NREL (DOE), General Electric Co. (NYSE:GE), The Hawaiian Electric Company, and the Hawaiian National Energy Institute on behalf of the Hawaii Clean Energy Initiative (HCEI). It is the first highly detailed dataset to examine the effect of clouds on solar PV panels.

The data can be found on NREL’s Measurement and Instrumentation Data Center (MIDC) website, under the seventh line item, SOLRMAP: Kalaeloa Oahu. The direct link is here.

,h1>Original Article on Energy Boom


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