A self-sufficient home with solar panels installed only on its facade

June 5, 2017
A self-sufficient home with solar panels installed only on its facade
The public will be able to discover the NeighborHUB, now finished, Saturday June 10th in Fribourg. Credit: Swiss Living Challenge / EPFL / 2017

EPFL, in association with the School of Engineering and Architecture of Fribourg, the Geneva School of Art and Design and the University of Fribourg, is taking part in the 2017 international Solar Decathlon competition. Students have designed a house called NeighborHub that gets all its energy from solar panels installed only on the building's facade. NeighborHub will open its doors to the public next Saturday.

Can a home run entirely on solar facades? Apparently so, according to NeighborHub, a house designed and built for the 2017 Solar Decathlon by Swiss students from EPFL, the School of Engineering and Architecture of Fribourg (HEIA-FR), the Geneva School of Art and Design (HEAD Genève) and the University of Fribourg (UNIFR). With NeighborHub, the students wanted to show that it makes both practical and economic sense to install solar panels on a home's facade – thereby maximizing the surface area put to use – even though sunlight can sometimes struggle to penetrate urban areas. "Unlike rooftops, facades are more likely to be in the shade since other buildings can block the sunlight," says Philippe Couty, the engineer coordinating the project for HEIA-FR. "That could sharply reduce the amount of power that solar panels generate. But we wanted to show that solar can indeed be produced on facades, even in areas packed with a lot of buildings." The project team went about searching for technology that could prove them right. Peter Cuony, head of solar power systems at Groupe E Connect and a member of the project team from the very beginning, came up with the idea of using power optimizers. The students found that these optimizers fit the bill perfectly, and they installed one in each panel to continuously monitor and adjust the solar panels' performance.

Maximizing each panel's output

In conventional , the panels are connected in series, which means each one can generate only as much energy as the lowest-producing one. Power inverters, taking their cue from the least productive panel, convert the direct current into the alternating current that the home can use. But this method can be a major handicap for the efficiency of solar panels installed on facades, since the weakest link (e.g. the most shaded panel) could pull down the entire system's power generation. And that was exactly what happened before the power optimizers were installed on each panel. "Even if each panel has a different level of sun exposure and consequently generates a different amount of energy, the optimizers draw on the instantaneous maximum of each panel, regardless of how much sunlight they do – or don't – receive," says Victor Saadé, an EPFL electrical engineering student who is leading the project group responsible for solar panels.

Achieving energy independence

Thanks to this novel way of using existing technology, NeighborHub can run entirely on the power generated from its facade-installed solar panels. It even generates more energy than it needs. What's more, its rooftop remains free for other purposes, like promoting biodiversity – the space can be used to cultivate a variety of plants.

The energy independence achieved by the one-story house offers encouraging prospects for residential buildings. Each story could generate enough for its own needs. That could be a major benefit for cities that are growing vertically."Our house demonstrates that it is possible to produce enough energy for an entire building using installed only on the building facades," says Cuony.

Explore further: The school with the largest solar facade in the world

Related Stories

The school with the largest solar facade in the world

February 10, 2017

he Copenhagen International School's new building is covered by 12,000 colored solar panels based on a technology developed at EPFL. It is one of the largest building-integrated solar power plants in Denmark.

Solar panels repay their energy 'debt': study

December 6, 2016

The climate-friendly electricity generated by solar panels in the past 40 years has all but cancelled out the polluting energy used to produce them, a study said Tuesday.

Yale engineer to build 'hot' solar cells

September 22, 2014

Associate professor of electrical engineering Minjoo Larry Lee has been awarded $2,540,000 to develop dual-junction solar cells that can operate efficiently at extreme temperatures above 750 degrees Fahrenheit. In addition ...

Recommended for you

Enhancing solar power with diatoms

October 20, 2017

Diatoms, a kind of algae that reproduces prodigiously, have been called "the jewels of the sea" for their ability to manipulate light. Now, researchers hope to harness that property to boost solar technology.

Dutch open 'world's first 3D-printed bridge'

October 17, 2017

Dutch officials toasted on Tuesday the opening of what is being called the world's first 3D-printed concrete bridge, which is primarily meant to be used by cyclists.

14 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Eikka
5 / 5 (1) Jun 05, 2017
In conventional solar power systems, the panels are connected in series, which means each one can generate only as much energy as the lowest-producing one.


That is a competely inaccurate description of how solar panels work.

If one panel in a series is shaded, the voltage of the series drops by one panel, but all the other panels still work and force current through the shaded panel. That reduces efficiency, but does not limit production to equal the shaded panel. In practice, each panel will have a bypass diode just for this case, which allows current to route around the weak panel, because the current forcing would otherwise heat up and possibly damage the shaded panel.
Da Schneib
not rated yet Jun 05, 2017
Actually, @Eikka, there are multiple setups, series, parallel, and series-parallel. Which one you use depends on your inverter's input range, and the outputs of the panels. And, in this case, considerations having to do with one or more panels not putting out as much because it's in shadow.

The text in the article is overly simplistic, I agree. Note however that the setup seems to work fine and produces plenty of power.
Eikka
5 / 5 (1) Jun 05, 2017
Actually, @Eikka, there are multiple setups, series, parallel, and series-parallel.


True, and in each one you have blocking and bypassing diodes to prevent current backflows through weaker parallel strings, and for routing around panels which do not contribute equal amounts of current. It is common to have bypass diodes already built-in to panels, while blocking diodes depend on the whole system configuration.

An optimum design would have equal output in all panels - in practice no combination works perfectly all the time. The MPPT controller is then supposed to find the combination of current and voltage which produces the largest output power at any given moment, and invert it to AC for the home.

They are not describing anything new, except perhaps using an MPPT for each individual panel instead of the whole system, which is simply trading money for efficiency, since the bypass/blocking diodes incur a certain loss due to their forward voltage drop.
Eikka
5 / 5 (1) Jun 05, 2017
Power inverters, taking their cue from the least productive panel, convert the direct current into the alternating current that the home can use.


This is completely wrong. The power inverter does not know the panel configuration - it does not know which panel is the weakest or how weak it is, and it doesn't need to. It simply tries to draw different amounts of current to see what happens to the total voltage of the panel system.

In essence, it tries to maximize voltage and current by trial and error - at best these systems have a sensor to measure the general lighting level to detect clouds passing by because the settling time may be too long to respond to fast transient changes in sunlight - and the blocking/bypassing diodes make sure the individual panels don't get in each other's way.
tekram
not rated yet Jun 05, 2017
The winner will be coming to the US, October 5 – 9 and 12 – 15, 2017 at the 61st & Peña station near Denver, Colorado's International Airport,

The Swiss team selected for the 2017 edition, is made up of participants from the Ecole Polytechnique Fédérale de Lausanne (EPFL), the School of Engineering and Architecture of Fribourg (HEIA-FR), the Geneva School of Art and Design (HEAD) and the University of Fribourg (UNIFR). In the fall of 2017, the team will take its prototype to Denver, Colorado, where they will exhibit the design to professional juries and the general public.

http://www.swiss-...e.ch/en/
Eikka
5 / 5 (1) Jun 06, 2017
Note however that the setup seems to work fine and produces plenty of power.


Maybe, but it's not a very economical way to utilize the solar panels themselves, considering they're placed in sub-optimal angles and get shaded much of the time. It seems to be a solution looking for a problem - what's wrong with having the panels on the roof?

And in climates where it rains, buildings have long eaves which shade all the panels for the middle of the day during the best production hours.

Every time the architects get the brilliant idea of designing "functionalistic" homes with flat or only slightly slanted roofs and short eaves, they become mold bombs and rot away in two decades. They forget Einstein's wisdom: "Everything should be made as simple as possible, but not simpler."

antialias_physorg
5 / 5 (1) Jun 06, 2017
Full facade solar setups are viable.
The 2009 winner of the solar decathlon already featured a full-facade solar cell setup
https://www.solar...any.html
...which produced 200% of the house's need (even over-producing during cloudy weather). So the amount of backup storage was reduced to a few hours of night time use which could be handled locally by in-house tech. No grid or large scale energy backup needed.
Eikka
not rated yet Jun 09, 2017
Full facade solar setups are viable.
The 2009 winner of the solar decathlon already featured a full-facade solar cell setup
https://www.solar...any.html
...which produced 200% of the house's need (even over-producing during cloudy weather). So the amount of backup storage was reduced to a few hours of night time use which could be handled locally by in-house tech. No grid or large scale energy backup needed.


So they got 11 kW on the roof, and all the sides covered in CIGS panels which contain Indium which is expensive and in short supply. Total costs estimate $650,000-$850,000

Wow.

The total power of their panels according to the papers 17.76 kW of which 11.1 kW is placed on the roof. Roof-mounted panels in Germany achieve a capacity factor between 7 - 11% depending on location, so their year-round output average should be around 1.5 kW.

If that is 200% the power demand of the house, then I don't believe it.
Eikka
not rated yet Jun 09, 2017
The difference can be explained - as I've pointed out many times before - by the fact that only around 5% of German households have electric heating. Most of them heat by gas and oil, so the electricity demand is low.

To power a home, you need to consider its full energy demand, not just some individual appliances - that would be cheating. The electricity demand of a German household is 3,500 kWh a year, but 75% of the actual energy demand goes to space heating, and another 10% to water heating which is also typically done on gas, pushing the real figure up to somewhere between 14,000 - 18,000 kWh/a

1.5 kW average output would be 13,140 kWh/a so the solar panel system might just about cover the energy demand of the average household. The 200% figure seems to come about because at times it's making more than what can be used, and conversely at other times less than is needed - supply does not meet demand.

So there's more to the story than meets the eye.
MR166
not rated yet Jun 09, 2017
Eikka thanks for your constant no nonsense analysis of articles like this. I would like to add 3 things. Heating requirements of a home can be substantially reduced with new insulating techniques. Also, in reality most people would not want to live in a home covered by solar panels so the roof makes a lot more sense if one has a roofing system under the panels that has a sufficient lifetime. Lastly, if they are siting this home in the middle of a barren parking lot it will get a lot more sun than the average landscaped home located close to neighbors.
MR166
not rated yet Jun 09, 2017
"That could be a major benefit for cities that are growing vertically."Our house demonstrates that it is possible to produce enough energy for an entire building using solar panels installed only on the building facades," says Cuony."

That statement is a prime example of eco-babble. If an area is growing vertically then buildings will shade the sides of each other and only the roofs will get sunshine.
MR166
not rated yet Jun 09, 2017
I remember when teachers prided themselves in being able to teach students how to think. Now, it seems, that they take pride in teaching students what to think.
MR166
not rated yet Jun 10, 2017
Humm, 4x the amount of panels for say 1/2 the output of a roof unit. It's a good thing that solar panels and their associated wiring are free because otherwise the whole idea would make no sense.
MR166
not rated yet Jun 10, 2017
"What's more, its rooftop remains free for other purposes, like promoting biodiversity – the space can be used to cultivate a variety of plants."

Just more eco-babble, it is very expensive to construct and maintain a roof that can accommodate a sizable garden.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.