Observing the renewable energy transition from a European perspective

Archive for the category “space heating”

“2226” – Heating with Light, Humans and Devices Only

German language video, Lustenau, Austria.

Passive heating in Austria. Temperature all-year around guaranteed to be between 22-26 C, hence the qualifier “2226”. Office building with 100 work places. Humans themselves are “hot” and serve as heat sources of 80 Watt. And so are devices like computers, lights, coffee machines, printers, etc. The trick is to keep this modest amount of generated heat inside the walls, that are no less than 76 cm thick.

The windows are deep inside, to prevent that too much solar heat will penetrate into the building in the summer, eliminating the need for cooling with energy devouring air conditioners. If inside, the temperature gets too hot or the air too stuffy, valves in the outer walls are simply opened. No complicated network of pipes and pumps is installed. The resulting building is cheap and simple and hence low-maintenance.


So where’s the catch? An important point is to let go of the superfluous wish to completely control the temperature at say 22 C. By tolerating the temperature to vary between 22 and 26 C, you gain a lot of freedom to eliminate both heating and cooling and leave it to inhabitants to decide to work in a t-shirt or pullover. Another important point is the relatively large thermal mass inside the building, that acts as a buffer and temperature stabilizer.

German language video with English subs. Example Luzerne, Switzerland.

[] – Keine Heizung, trotzdem 26 Grad – das System „2226“ macht Bauen einfacher
[] – Lochziegel

German language video, Burgenland, Austria. If works for detached homes too.

[source] Building elements for a 2226 building

Hydrogen District Hoogeveen

Hydrogen central heating boiler

In Hoogeveen in the Netherlands, a group of 100 new homes will be equiped with solar panels and electrolyzers to produce hydrogen in the summer. During the heating season the hydrogen will be pumped into the homes from a central storage and converted into low temperature heat for space heating. The hydrogen will be fed into the homes using regular natural gas pipes (see picture above).

If this project will be successful, next a neighboring district named “Erflanden” (1200 homes) will be retrofitted for hydrogen heating as well, replacing conventional natural boilers with hydrogen ones, using the old natural gas grid. This project is a front-runner and one of the most advanced in the world.

[] – Project site
[] – Eerste waterstofwijk in Nederland komt in Hoogeveen

Read more…

Ecovat Status Update

Ecovat is one of our favorite renewable energy concepts.

Current portfolio Ecovat (Jan 2020):

Panningen (Peel & Maasland), pre-engineering project, 500-750 homes
– Heerlen 2,000-3,000 homes
– Apeldoorn, pre-engineering, 4,300 homes
– Deventer, Zutphen & Zwolle (“Transform“), pre-engineering, 48,000 homes

Apart from a demonstration, the first real project has yet to be built. We hope this happens soon.

Come on Dutch municipalities, stick your neck out and help a Dutch potential key-technology to get launched.

[] – Voortgang & update Ecovat projecten (Jan 2020)
[] – Arnhem-Siza (“Het Dorp”) Ecovat afgeblazen (Jul 2019)
[deepresource] – Our Ecovat posts
[] – Ecovat missing link voor duurzame energie
[] – Ecovat zoekt geld voor expansie (Apr 2019)
[] – 1613 – 02 Hijsframe design (voor Ecovat)
[] – ‘Vergeten’ besparing Ecovat (Jul 2018, link to 16p pdf)
[] – Ecovat voorbeeld van energietransitie naast de deur
[] – Huizen verwarmen met een reuzethermosfles (Jul 2019)
[] – Ecovat verhuist naar de Poort van Veghel (Okt 2017)

Over drie jaar wil De Groot een leidende rol in Europa in thermische energieopslag. Het team van Ecovat betrekt daarom de hele zesde verdieping van Toren I, het pand direct aan de A50.

[] – Warmteopslag in basalt voor het ECOdorp in Boekel

Het voorgestelde Ecovatsysteem voor de Trekvlietzone in Den Haag voorziet een vat van 40.000 m3, goed voor 2500MWh, voor investeringslasten van 6 a 7 miljoen. Zit dus ergens rond de 2,5 cent/kWH, maar er is dus een kant en klaar plan, duizend keer zo groot. ECovat werkt met water van 90C en oogt iets beheersbaarder. De energiedichtheid bij ECovat zit op ongeveer 0,22GJ/m3 . Na een half jaar is nog ruim 90% van de opgeslagen warmte over.

New Ecovat Production Line Video

[deepresource] – Our Ecovat posts

District Heating in the Netherlands

In line with the 100% decarbonization policy of the European Union, to be achieved by 2050, the Netherlands is busy moving away from space heating with natural gas towards district heating with process heat, biomass and/or heat pumps. New-build homes in the Netherlands are by law no longer connected to the national natural gas grid.

A large number of small companies are picking up the new opportunities in the Netherlands to construct district heating warmtenetten. Companies like Twence or Warmtenet Dordrecht that currently has 3,000 homes connected and aspires to achieve 15,000 eventually.

Another example is the city of Eindhoven, the home base of Ennatuurlijk:

Blue lines indicate areas that already have district heating. Ennatuurlijk plans to expand further throughout Eindhoven.

[] – Ennatuurlijk
[] – District heating
[] – Twence corporate site
[] – Warmtenet: op naar de 15.000 huizen in Dordrecht
[] – warmtenet Dordrecht

Read more…

Inventum – Ecolution Solo

It’s difficult to equip an older home with a heat pump, that operates at lower temperatures and as a consequence needs floor heating. A good compromise can be to combine a smaller heat pump in series with an existing boiler and let the heat pump do the preheating. 35% energy reduction is claimed by Inventum.

[] – Warmtepompen
[] – Inventum Ecolution Solo KA01697
[] – Mini-warmtepomp mikt op massa

The input is air from within the home, output hot water in the radiator.

Real review: heat pump installed in the attic. 50% less gas in November, minus the additional electricity cost. The 35% claimed by Inventum could be true.

Hybrid Solar Collectors & Heat Pump

(Dutch language video)

In our view, photovoltaic thermal hybrid solar collectors (PVT) are one of the most underestimated renewable energy harvesting solutions in places where space is rare and expensive. Think countries like the Netherlands. In a solar panel, a typical 20% of the solar radiation is transformed into electricity. In an isolated black flat plate solar thermal collector, the absorption rate is near 100%. In oractive typical values are: 250 kW electricity plus 400 kW heat, and operating with 80% overall conversion efficiency. In a hybrid PVT-panel/collector the photo-electric and thermal functions are combined in one. In the examples presented here, the thermal collector functions as the source for a heat pump. This is an alternative to more conventional solutions as extracting heat from a much colder source like 10 Celsius soil. The roof rather than the garden, so to speak.

In the Netherlands it is no longer allowed by law to build new homes with a natural gas connection; hence tens of thousands of new homes every year come with a heat pump installed. The battle for the most advantageous heat source for the heat pump has been ignited: soil, air or PVT-roof. May the best solution win.

[] – Photovoltaic thermal hybrid solar collector
[Google Maps] – Waalre
[] – Volthera hybrid solar collector
[] – Warmtepomppaneel
[] – Triple Solar PVT Heat Pump Panel
[] – PVT: het dak als warmtepompbron

A similar example in Schildwolde, Groningen

TNO & TUE Heat Battery

Dutch video, English subs

TNO and TU/e have developed a brand new device principle and a breakthrough material, in which the heat is stored. Together they form the heat battery. It is so small that it fits into the limited space available in most homes. The breakthrough material is a salt composite, with K2CO3 (potassium carbonate) as the base material.

The heat battery uses a so-called thermochemical principle. The heat battery for the home is based on two components: water and a salt hydrate. As soon as water vapour and salt are added, the water binds to the salt and the salt transforms into a new crystalline form. This reaction that releases heat is reversible. When heat is added to separate the water from the new crystal, the two original components are obtained again. In fact, it is this heat that is stored, and as long as these two components are separated, the stored heat is retained. This makes it a process without heat loss, which in turn is a prerequisite for long-term storage of heat. In this way a lot of heat can be stored in a small volume. Significantly more than water, and considerably more than in so-called phase transition materials.

The battery can store both heat and electricity. It has the size of a small refrigerator, expected consumer price 3,000-6,000 euro. Technical life expectancy 20 year. Storage capacity device: 200-300 MJ (600 MJ/m3). Power: 1-3 kW. The battery has 4 parts: ventilator, heat exchanger, condensor and reactor vessel:


The heat capacity is at least ten times higher than that of water and more than phase-change-based devices.

[] – A Heat Battery For The Home: Compact, Stable, and Affordable
[] – Miljoenensubsidie EU voor innovatieve warmtebatterij
[] – Thermal battery

The European Commission has granted a 7 million euro subsidy for further development of the TNO and TUE heat battery, within the Horizon2020 framework. For that purpose a new European consortium named HEAT-INSYDE, led by TNO and TUE, will develop the heat battery for the consumer market.

[] – Horizon2020

[source] Prototype heat battery

Self-Heating Building with Algae

Renewable energy is generally associated with windturbines and solar panels. It is often ignored that electricity is only part of the entire energy story. In northern Europe for instance an average household needs to pay more for space heating than for electricity on a yearly basis. The BIQ building in Hamburg could provide the solution for an energy-neutral home that collects solar energy all year around and stores part of the solar energy in the form of algae. The algae biomass can be used for gas production and is easier and cheaper to store than warm water. Up-front capital costs are high though: $2500/m2. Reduction on fossil fuel cost to date is 33%. This number could increase if solar panels are placed on the roof, used to produce electricity to power heat pumps.

[] – This Algae-Powered Building Actually Works (2014)
[] – Tomorrow’s architecture, starring algae and hemp (2016)

Thermo-Acoustic Heat Pump


The Dutch national energy bureau ECN has build the prototype of a heat pump that is smaller than conventional heat pumps and potentially could become even a lot smaller. What is special about this heat pump is that it operates on sound. Sound is a pressure wave. If air is compressed it gets warmer. The ECN heat pump is a closed tube with speakers.

Core parameters: heat pump is a wall-mounted box of 40x50x10 cm. You need electricity for an air pump and speakers. Electricity of 1 kWh returns 4 kWh of heat. Air is pumped from outside and led through the (inaudible) “sound heat pump” and finally pumped into the living space, providing ventilation as an extra.

Within the Dutch context that means that you get the same heat performance from 2 kWh (40 cent) as from 1 m3 gas (64 cent). Eventually that heat pump can be powered by electricity from renewable sources. The heat pump should cost ca. $1,000 including installation.

[] – Warmtepomp van ECN wordt de nieuwe gevelkachel
[] – Thermoacoustic heat engine

At [1:00] the sound-heat conversion is demonstrated. Sound in the tube pumps heat from lower to higher temperatures.

The thermo-acoustic principle in reverse: use heat to generate standing sound waves and create mechanical work.

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