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A grid-hybrid approach key to mainstream renewable energy adoption


September 13, 2016
By Anthony Capkun


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September 13, 2016 – At the Université libre de Bruxelles (ULB), researchers have concluded energy self-sufficiency in homes with solar PV panels and batteries may come with an expensive price tag, and there may be better solutions out there to go green.

In Belgium, two ULB researchers—Guilherme Silva and Patrick Hendrick—report solar photovoltaic systems coupled with lead-acid batteries currently do not ensure the electrical self-sufficiency of a residence at a reasonable cost. Their simulations reveal the maximum rate of self-sufficiency of solar panels would only be about 40%, while the addition of complementary lead-acid batteries would result in a considerable increase of the energy prices.

Silva and Hendrick started by crunching up-to date Belgian data from the Royal Meteorological Institute, energy suppliers and installers, then ran these numbers through their simulation models before concluding it may be a while before we can all afford to go off-grid.

The problem starts with the well-known bad timing of solar energy and its consumption: while the sun shines at its maximum around midday, most homes consume the most in the morning and in the evening. Add to that the fact that, in many countries, most of the solar energy is available in the summer months, and you’re set for dark times. No matter how many solar panels are added up, the maximum attainable self-sufficiency will be around 40%, say the researchers.

The good news is that 40% self-sufficiency is achievable at a price comparable to the grid, given the decreasing cost of solar panels and their life spans. To go beyond 40% self-sufficiency, energy storage seems the natural answer. The researchers coupled the solar panels with lead-acid batteries and, suddenly, the energy consumed becomes really expensive.

Trying to reach a self-sufficiency of 60% can easily cost twice as much as using the grid. And the batteries’ short life spans and high price are not the only ones to blame: installation costs and the additional electrical equipment required also play a role.

The researchers also took a look at the impact on the power grid of solar panels and home energy storage, and the results seem grim. Homes equipped with such systems place a greater strain on the power grid. Also, power plants will need to be able to answer to quicker variations in demand. All this will impact power grid prices, a field where research is still lacking.

However, the researchers’ conclusions are not all doom and gloom: they say a hybrid approach must be adopted for sustainable energy use. Using several energy sources helps to balance out each one’s disadvantages. Consumption can also be adapted through intelligent appliances that can adjust to current conditions. Recent energy storage technologies—such as li-ion batteries—continue to enjoy strong price reductions, note the researchers, while the share of electric vehicles continues to increase.

Meantime, Silva and Hendrick say there is no magic bullet, and the best option is to keep some solar panels while continuing to use the grid.