East-west rooftop solar ideal for energy communities under net metering – pv magazine International

June 4, 2024 Emiliano Bellini

A group of researchers led by the Politecnico di Torino in Italy has investigated the optimal orientations and tilt angles for PV systems used in energy communities and has found that east-west oriented arrays provide higher shared energy values than south-oriented installations.

East-west orientation is commonly thought to be more suitable for high latitudes with low solar radiation, enabling the use of sunlight in the first and last hours of the day. These projects, however, may also be the ideal solution in tropical locations or in areas with limited available surface area, such as commercial rooftops.

First, the east-west solar panel configuration produces a more stable and consistent output throughout the day compared to a conventional south-facing installation. In addition, it reduces the central power peak at midday and extends the duration of solar production in the early and late hours of the day, with the solar panels beginning to produce at sunrise and continue producing until sunset. This makes the systems preferred by grid operators as power is supplied more evenly throughout the day; but it also encourages residential self-consumption in the afternoon, when users are more frequently at home.

In addition, shadows are avoided between rows of solar panels. By contrast, installations with solar panels facing south produce shadows from the front rows on the rear rows. Thirdly, in east-west arrays, the more compact installation of solar panels increases the density of energy production per m2. This is especially attractive on small roofs where this system allows up to 30% more density per square meter.

Another notable point is its greater tolerance to wind. With an inclination angle of 15 degrees and an east-west configuration, the wind pressure is drastically reduced compared to a south-facing configuration, much more vulnerable to north winds. An aspect derived from the previous point is that, due to less exposure to wind, east-west solar systems need much less counterweight to secure the solar panels to the roof. This allows installation on less robust roofs, or on roofs with other facility installations.

In the paper “Shared energy in renewable energy communities: The benefits of east- and west-facing rooftop photovoltaic installations,” published in Energy Reports, the Italian research group explained that PV tilt angle is often neglected in the scientific literature about energy communities, stating that the novelty of their work consisted of outlining rooftop geometrical parameters on the synchronism between generation and demand profile for different orientation and tilt angle. They also specified their modeling was based on the assumption that the PV systems of the energy community have the option of selling surplus power to the grid under a net-metering regime, and that the community is formed by households sharing the same point of common coupling.

Through a Monte Carlo simulation modeling, the group analyzed an energy community of 60 users relying on PV systems totaling 150 kW, with the arrays being owned by 30 users. “All results from the simulations are presented with a 95 % confidence interval, emphasizing the statistical reliability of our findings,” the academics stated. “Moreover, under the assumption that the PV systems align with the orientation of the rooftop on which it is installed, all PV have same orientation and tilt angle.”

The analysis showed that, although the simulated community using south-oriented PV systems is able to achieve higher energy yields, the community based on east-west arrays offers the advantage of higher shared energy values, which the scientists said depends on better synchronicity between demand and PV power generation during early mornings and late afternoons. “The energy self-consumed virtually by the energy community achieves the highest value for southward PV orientation at the expense of higher injection peak into the grid,” they further explained. “This is a significant aspect in contexts where the absolute shared energy within the energy community is explicitly incentivized, such as in Italy.”

They also pointed out, however, that their findings may not apply to scenarios with high PV penetration without net metering schemes in place. “Our investigation was confined to a single location. While this specificity allows for a detailed analysis, the results might be influenced by variations in PV yield from other regions,” they also warned.  “The results advocate for a more inclusive approach in the design and planning of energy communities. Rather than an undue emphasis on south-faced rooftop PV installations, a diverse range of orientations and inclinations should be considered.”