INTRODUCING SOLAR POWER FORECASTS
MetService is pleased to begin producing solar power forecasts for the Auckland region, as part of our partnership with HRV.
WHAT DO OUR SOLAR POWER FORECASTS PREDICT?
The daily solar power forecast on the Auckland page is a prediction for the total amount of electricity that will be produced by all the solar panels installed across the Auckland region. These forecasts are issued in a commonly used unit for solar power: kilowatt hours (kWh).
WHAT IS A KILOWATT HOUR?
A kilowatt hour (kWh) is a unit of energy. It quantifies the amount of electricity that would be generated by a 1kW solar panel system in one hour, under optimal conditions. One kilowatt hour is about enough power to run a laptop computer for 24 hours, boil a kettle 7 times, or heat up leftovers in the microwave 20 times.
Another commonly used unit is the megawatt hour (MWh), which is equal to 1,000 kilowatt hours.
HOW DO SOLAR PANELS PRODUCE ELECTRICITY?
The sun emits an immense amount of electromagnetic radiation, which we perceive as both light and heat. This solar radiation consists of a vast spectrum of wavelengths which can be divided into several defined bands, such as infrared, visible, and ultraviolet.
Solar panels are designed to capture solar radiation that is mainly in the visible spectrum. This is because solar radiation naturally peaks in the visible light spectrum, and thus proves to be the most efficient band of sunlight to capture. When exposed to sunlight, solar panels create electricity by converting that sunlight into an electric current. This is called photovoltaic (PV) power generation.
Ultraviolet (UV) radiation is not visible to the human eye, and is a negligible component of the solar radiation captured by solar panels. Overexposure to UV radiation is the cause of suntan, sunburn, freckling, and a higher risk of skin cancer.
HOW DO WE FORECAST SOLAR POWER PRODUCTION?
Predicting Solar Radiation
The first step in our forecast process is predicting the total amount of solar radiation that is expected to fall across the Auckland region. This is predicted using data acquired from numerical weather models – which considers atmospheric conditions such as cloud cover, cloud density, and atmospheric water content – to predict the total amount of solar radiation expected across the entire forecast day. If we are forecasting for a region, then a forecast is produced by taking a weighted average of forecasts from various locations within that region
Converting to Solar Power
The next step is to convert this prediction of daily solar radiation into a prediction of the amount of electricity that would be produced by an individual 1kW solar panel when it is exposed to this amount of solar radiation over a day. Our conversion factor is calibrated against real world installations, which means our forecasts are not tuned to optimal conditions, but instead are representative of the typical conditions of the various solar panels across the country.
Forecasting for houses, regions or countries.
Finally, our forecasts are multiplied by the number of 1kW solar panels we are predicting for. This allows us to predict the solar power expected to be generated from a single household, a region, or the entire country. For our Auckland regional forecast we use the installed capacity figures available from EMI.