Observing the renewable energy transition from a European perspective

Archive for the category “heat pump”

Stirling Heat Pump

[] – Stirling engine

Affordable Sustainable Living in Aalst, Netherlands


There are too many sustainable projects in the Netherlands to keep track off, nevertheless, this one is singled out for 2 reasons:

1. application of PVT-panels
2. affordable for lower incomes

(There is a third reason that doesn’t apply to you, namely that this project is less than an hour walk from yours faithfully’s own home, so worthy of a detour for the daily self-imposed 10,000-step stroll)

The project scope: 25 energy neutral social housing rental homes. Delivery March 8, 2021. Excellent thermal isolation. Part of the building materials were recycled from the old torn-down homes. The basic rent: €630,- for 2- or €675,- for 3-bedrooms, which is low. Additionally, there is an energieprestatievergoeding (EPV) of about €105-125/month, a sort of compensation for the landlord and his energy investments. In return, the tenant hardly has an energy bill left.

The downside is that comfort is reduced. It takes 24 hours to bring the home at a temperature of 21 C. The heat pump capacity is low. In the rare case of freezing weather, inefficient additional heating is done with filaments. Electricity and heat are generated with PVT-panels.

[] – Duurzaam wonen aan Michiel de Ruyterstraat in Aalst is ook even wennen
[] – Michiel de Ruyterstraat, Aalst-Waalre
[] – Energieprestatievergoeding (EPV)
[] – Project plan
[Google Maps] – Michiel de Ruyterstraat, Aalst

[Google Streetview] – Shows the situation before the renovation

Neighborhood before the renovation.

Woning van het Gas af met Warmtepomp en PVT-Panelen

Bodemwarmtewisselaar voor Warmte- en Koude Opslag

Energy Quay Walls

The Netherlands are an extremely water-rich country, with more than 5,000 km navigable waterways/canals. They come with more than 10,000 km quay walls (Dutch: kademuren).

Many of them made from steel.

Typical Dutch situation: canals demarcated by steel plates, that can serve as “energy walls”

Steel is a very good thermal conductor, much better than soil. Here is the idea: mount steel pipes to the steel quay walls and ensure good thermal conductivity. Pump a suitable fluid through the pipe-network and use it to extract heat from the canal and use it as input to heat pumps. The energy harvesting potential is considerable. Estimated COP values: up to 5-6 and can be used for both heating and cooling. Power: 500 Watt/m2. The quay walls are existing infrastructure and can be upgraded at relatively low cost.

[] – Energie winnen uit stalen damwanden
[google maps] – De Zweth
[] – Contractor Crux BV
[] – German partner and patentholder
[] – Gooimeer BV produces quay wall in license

Read more…

VattenFall-Feenstra High Temperature CO2 Heat Pump

Vattenfall and Feenstra will bring a new heat pump to the market, designed to operate at high temperatures (70-90 C), that can function as a direct replacement for any conventional natural gas-fired central heating system, eliminating the need for low temperature floor heating. Instead you can continue to use your old but functioning radiators. Essential in the new setup is a temperature-layered buffer vessel. Power: 6 kW base, 11 kW peak.

Conventional heat pumps operate best at temperatures in the range of 35 C. This new heat pump uses CO2 as medium, using high temperature in, higher temperature out. Field tests are underway in 20 homes. If successful, first installations will become available by the end of this year. Realized HSPF values in the order of 3.0.

[] – Bestaande woningbouw eenvoudig aardgasvrij met nieuw hoge-temperatuur-warmtepompsysteem
[] – Testresultaten CO2-warmtepomp voor woningen veelbelovend
[] – Heating seasonal performance factor
[] – Coefficient of performance

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…

Sewage as the Heat-pump Cold Side


Homes can be heated much more energy efficient with a heat pump than a conventional CV-with-boiler. Heat-pumps pump heat from a source to the target, your home. That source can for instance be air, or a pipe-grid buried in your garden. The trouble is, in the winter the air is cold, where the heat pump works best with the smallest possible temperature difference between source and target (21 C). The magic formula in the world of heat pumps (and your fridge is one of them) is:


Q is the heat we want to pump in your living room, W is the “Work” (preferably emission-free renewable electricity) we need to get the heating job done.

The relationship between the lower temperature of the source TL and the higher temperature of your living room TH is:


Under good conditions COP values of 4 or higher can be achieved. A COP-value of 4 means that with a heat pump and 1 unit of electricity we can achieve the same heating result as with 4 units of electricity in a electric heater. “Good conditions” means: a as high as possible source temperature. Air in the winter can be 0 C or lower. The soil in temperate climate like NW-Europe is something like 10 C, which is already much better. The point is though that soil is a bad heat conductor, meaning that as you gradually extract heat from the soil, the temperature of the soil decreases, as the surrounding soil is not able to keep the temperature constant fast enough.

That is where the sewage idea comes in. Temperature sewage water: 10-15 C, which is high. And it flows! Meaning, there is a constant supply of (smelly) water of 10-15 C!. Brussels is now contemplating to use the sewage fluids as a heat source. In Raalte in the Netherlands they already have a swimming pool heating system working based on this idea. In Brussels and Raalte they have smelled a rat… err smelled the coffee!

[] – Can we heat buildings without burning fossil fuels?
[] – Sewage water heating pool water
[] – Heat pump and refrigeration cycle

The Raalte swimming pool has been heated with sewage heat since 2013. From the nearby sewage treatment plant, ‘clean’ sewage water with a temperature of 10-15 degrees Celsius is pumped towards the pool. Heat exchangers are installed in the pipes. The pool water is then brought up to temperature with a heat pump.

Sewage in Dutch is “riool”. Hence the word “riothermal”, prompting associations with the Copacobana rather than your toilet. In 2018 three Dutch swimming pools are heated this way (COP 5-6) and claim to be the world’s first. Additionally in Goes they are building a system for 60 homes:

The Goes project. Other pilot schemes exist in Amstetten in Austria, Glasgow in Scotland, and Rotterdam in the Netherlands.

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.

De Prijs van een Warmtepomp

[source] Lucht-water warmtepomp

Type warmtepomp Gemiddelde kostprijs [euro]
grond-water 10-25k
water-water 15k +
lucht-lucht 4-7k
lucht-water 4-7k
hybride 5-7k

[] – Kosten Warmtepomp
[] – Alpha Innotec SW-42 warmtepomp, 4 kW (7.345,- incl BTW)

Ground Drilling Vertical Heat Exchanger for Heat Pump

Realistic price calculation:

Freestanding house: 750 m3
Two-three drilled wells of 85 meter each in the garden, 6 meter apart
Temperature cold side: 12 degrees centigrade
Project size: two men, one day
Energy saving: up to 70%

[] – Average price tag:

Average residence, 8 kW heat loss and average geology, boiler 300 liter en floor heating 160 m2
Average space heating cost with natural gas for Dutch house-hold: 1,000 euro.

All-in prices for single household:

Soil-water heat pump with vertical heat exchangers: 20000 € excl. VAT
Soil-water heat pump with horizontal heat exchangers: 17000 € excl. VAT
Air-water heat pump: 14000 € excl. VAT
Subsidy: 1600 euro in 2018

Prices likely come down if you increase project scale. New homes will have no choice as proposed new regulation will forbid a natural gas connection for new-build homes. For the typical Dutch terraced houses, investment costs are lower.

[] – In the Netherlands there are 7 million households. Of these 160,000 do own a heat pump. Currently this number increases with 20,000 per year. As per 2021 this number will increase as all new buildings by then will be deprived of a connection to the existing natural gas grid.

Bauablauf GeoCollect-Erdwärme-Absorber-System

[] – Company site
[] – Preisliste
[] – Effizienter Erdwärmekollektor mit geringem Platzbedarf

Solar Panels and Heat Pump

Solar panels powering a heat pump for space heating.
17 panels in total, 7 for the heat pump.
The heat pump produces an input water temperature of 45 degrees Celcius, which suffices for most of the heating season.
Result: electricity neutral and more than 1000 m3 natural gas saved annually.

Dutch government 5 kW heat pump national subsidy: 1000 euro.

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