PlusEnergy Building Design 101 — Heliotrope, Solar Settlement, & Sun Ship

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Further building on our discussions of energy efficient building design — via the subjects of basic passive solar home design elements, the Passivhaus standard, R-value terminology, and earth-sheltered house design — it seems worth highlighting the “PlusEnergy” building design approach.

The “PlusEnergy” phrase was apparently first used by Rolf Disch back in 1994 when designing a private residence for himself that was later known as “The Heliotrope.” The basic idea, as predicted by the name itself, is for a building to produce notably more electricity than it uses (via renewable energy technology) and thereby serve as a local “power plant” of sorts while also serving the building’s own requirements. Alternately, the designation could be considered building with the Passivhaus energy efficiency standard, or as a sort of cousin of the NetZero standard.

Following the completion of Disch’s first PlusEnergy design, further concepts were developed and built by Rolf Disch Solar Architecture (Disch’s the architectural firm), including the “Solar Settlement” and the “Sun Ship.” The idea behind these somewhat ostentatious concepts was/is apparently to generate buzz and increase adoption of the PlusEnergy approach in the residential, retail, and commercial sectors.

Generally speaking, the PlusEnergy approach to building design draws on passive solar house design strategies, extensive insulation and near airtightness (Passivhaus), daylighting strategies, integrated solar PV system use, and awareness of transportation needs (bikesharing and carsharing services nearby or integrated).

That is to say, energy needs are meant to be minimized through passive solar energy captured in thermal mass during the day and retained through the use of good insulation — in combination with solar PV systems and a means of avoiding excessive heat gain during the warmer months. In the case of the Heliotrope, for instance, excessive heat gain during warmer months can be avoided through the building’s somewhat uncommon approach whereby the whole building can be rotated as to track the sun or avoid it, as need be.

On that subject … I’m now going to provide a basic overview of the 3 most publicized PlusEnergy concept designs created by Rolf Disch Solar Architecture — the Heliotrope, the Solar Settlement, and the Sun Ship.

Heliotrope — Rotating Passive Solar Building Able To Generate 4–6 Times Its Energy Needs Via Solar PV

Image by Andrewglaser (talk) • CC BY-SA 3.0

The Heliotrope was Rolf Disch’s first PlusEnergy design. It was built back in 1994 in Freiburg, Germany. The idea was not only for the structure to utilize only renewable energy but also for it to produce more electricity than it consumes by a notable margin.

As a result of those design parameters, the Heliotrope relies upon passive solar design principles in combination with a rotating base that allows the windowed side of the structure to be constantly in the sunlight — or not, as may be the desire depending upon the time of day and/or year.

In addition to passive solar design principles, effective insulation, triple-glazed windows, and near airtightness, the structure also features a very large solar PV array that can easily track the position of the sun. In addition, the building utilizes a geothermal heat-exchanger and an interesting solar-thermal balcony railing that’s function is to heat water. As noted above, as a result of the design elements relied upon, the building produces around 4–6 times as much electricity as it needs (varying by time of year).

A couple of other facts about the structure include: the inclusion of a waste composting system, a greywater reuse system, and the fact that it obviously is home to extensive views.

From the perspective of practicality and costs, of course, the Heliotrope is probably not a good design option except for those looking to grab eyeballs — which is presumably what Rolf Disch intended when he designed it. As far as producing far more electricity than you consume, the easiest means of doing so would of course be to greatly reduce one’s energy needs, followed by the possible implementation of a ground-mounted solar PV system where the panels can be made to track the position of the sun. That would no doubt be a far cheaper option, and likely a DIY option for many people.

A final note on the subject: in addition to the Heliotrope located in Freiburg, there have now reportedly been a few others built in Germany — at different scales and intended for different purposes.

Solar Settlement — Community Of 50 PlusEnergy Homes

Image by Andrewglaser (talk) • CC BY-SA 3.0

The “Solar Settlement” project was a project created following the completion of the Heliotrope that was meant to demonstrate the implementation of the PlusEnergy approach in the creation of a residential community. The basic idea was to create a project featuring 50 PlusEnergy homes, with these homes collectively generating far more electricity than they use, while buffering for each other’s electricity needs somewhat.

The Solar Settlement project was built in Freiburg, Germany — with completion occurring by 2005. The homes have on average been producing a surplus of a couple of thousand euros worth of electricity a year since full occupancy began.

Sun Ship — PlusEnergy Retail & Commercial Building

Image by Andrewglaser (talk) • CC BY-SA 3.0

Accompanying the development of the Solar Settlement community in Freiburg, Germany, a 60,000 sq ft (5,600 m2) retail and commercial space project dubbed the Sun Ship was also developed.

This “Sun Ship” is located right next to the Solar Settlement and is composed of a mix of retail space, commercial space, and some penthouses — with retail located on the first floor, commercial space just above, and residential on the top floors. The retail space has reportedly been occupied by a convenience store, a cafe, and a supermarket.

As with the other PlusEnergy designs discussed above, the Sun Ship utilizes effective insulation (via vacuum insulated walls and triple-glazed windows in this case), near airtightness, high-efficiency heat recovery ventilation systems, daylighting solutions (the north and south ends are essentially just windows on some floors), and an extensive integrated solar PV system.

The Sun Ship then, as one can see, seems to function as an adjunct to the earlier developed Solar Settlement — allowing residents of that project to do some of their shopping and/or work just a short walk away.

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James Ayre

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.

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