I’ve addressed this in part in the post on panels and orientation but it is worth exploring this in more detail as the use of farmland for solar in the UK is becoming just a contentious issue. There have been some articles in the press noting that reclassification of arable land could stop all deployment of solar on farmland which would have a significant impact not only on renewables but also on the viability of a lot of farms given the increasing energy costs and the withdrawal of EU subsidies following Brexit.
The French see agrivoltaics as one of the three pillars* of their solar strategy and this reflects that more fruit is being grown under protection film and nets. Some of this can be provided by solar panels with the high cost offset against the year-round production of electricity. They are also running an experiment where the panel orientation can be changed reducing the interruption to rain but restricting hail which can do a large amount of damage. This avoids the first point of contention in the UK which is the loss of arable land to solar farms. It also provides or offsets the cost of energy for the farmer to improve their situation.
This is before we get into the option of bifacial panels which was mentioned in the previous article about orientation. These have a small price premium to single-sided panels but have benefits in agrivoltaics deployment if mounted 2m off the ground to allow for plenty of light to be absorbed on the reverse side. While shade-tolerant crops benefit from monofacial panels. BP’s Loughtsoource has started to exploit bifacial panels as they give a 14% increase in energy generation for the same amount of area.
Then there is the benefit from the use of shade itself on the growth of crops which creates a symbiosis. On the whole, the productivity of an agrivoltaic installation is slighter higher than one where panels are not used but it depends on the crop and climate. One study found that in Arizona which suffers from very dry summers that the benefits from the shade lead to doubling the production of cherry tomatoes and tripling the production of chiltepin peppers. Even where it is not being used purely for agrivoltaics they can increase the diversity in the local ecology which has benefits.
The other benefit from reduced water evaporation and better water conservation. There are two benefits here as the water vapour condensing on the panels helps cool them which improves their efficiency as one of the issues with the current generation of panels is their output reduces for every degree above 25 degrees — again a symbiosis. The other benefit is from water conservation through a reduction in water loss from evaporation. Covering a section of California Aqueduct in America with solar panels indicated that 63 billion gallons of water could be saved from evaporating each year if applied across the state.
The bottom line is it shouldn’t be a case of one or the other but an and with solar supporting and complimenting farming.
*the three pillars of French’s solar strategy are rooftop, ground-mounted, and agrivoltaics.