Estimation 1 - Potential of balcony solar

In the first instalment of the estimation blog we'll have a look at estimating the potential for solar panels installed on the balconies of the building depicted below

Our aim is to estimate various quantities related to a solar installation for this building and we start with the simplest question:

How much power could this building reasonably generate if we were to deck each balcony with a permissible balcony solar installation?

It's a ~40 y.o. multi-tenant residential building in Germany with 12 floors and 8 (5 visible and 3 around the corner) balconies per floor.

The building's long axis is oriented N-by-W and it is pictured from the NNW direction.

Simple peak power estimate

Germany permits tenants an installation of an inverter with a peak output of up to 800 W. It does not, however, limit the power of the solar panels themselves. It is thus not unusual to be able to purchase exceedingly over-provisioned installations. We shall assume a simple set-up that can be bought off-the-shelf at a discounter (e.g. Netto) with a conforming power output. One can purchase a \(2 [kW_p]\) (the subscript \(p\) indicates "peak" power) installation with a buffer battery but that is an improvement we shall consider in a later step.

Now the simplest and very rough estimate for the peak power generation capacity of the building would just be

$$12 \left[ \text{floors} \right] \times 8 \left[\frac{\text{balconies}}{\text{floor}}\right] \times 800 \left[\frac{ W_p} {\text{balcony} }\right]= 76800 [W_p] \equiv 76.8 [kW_p]\;.$$

Which seems rather impressive! That's enough to run some 55 washing machines at a time.

We, of course, know that this estimate is naive. This assumes that all balconies are simultaneously maximally illuminated, which can not happen due to the orientations being towards West and South. Thus this gives us a rough estimate of what to expect.

Refinement

We can immediately refine our estimate!

While the building has 12 floors, at least on the present side we can only see 11 with balconies. The ground floor here has none. Since it's not visible in the image we should generously assume that there is a balcony or veranda on the ground floor at the S-by-E side not visible in the picture. Having to consider multiple cases will not be helpful for an estimation and we thus assume that having a solar installation on the ground floor would be unprofitable. This is justified by looking at the trees surrounding the building. These will provide a lot of shadow during the hot part of the year but severely reduce the production of electricity from solar panels on the ground floor. So we can immediately limit the estimation to 11 floors and thus obtain an estimated production of

$$ 70.4 [kW_p] \;.$$