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Search Results for: “ecovat

More on Ecovat

We admit to be fascinated by the potential of Ecovat, essentially a swimming pool of ca. 30 m deep and 70 m diameter, with a roof on it and concrete housing, well-hidden below the ground. These wind turbines, solar panels and solar collectors have meanwhile considerably matured, can compete with fossil fuel, so that aspect of the energy transition is in place. The remaining missing link is storage. Not storage in the hours range, like batteries or pumped hydro-storage, those are also maturing, but seasonal storage. Two approaches of seasonal storage exist: chemical and thermal. Ecovat covers the second option.

Remember that in Europe about 50% of the primary energy is used for heating purposes. That sector can be decarbonized with large bodies of warm water, water that can be brought up to temperature (90 C) with solar collectors and heat pumps. These heat pumps can be powered by intermittent renewable electricity. The beauty is that it doesn’t matter when that renewable electricity is available, like for instance at night, with everybody “on one ear”, since an Ecovat can keep its water warm for 6 months and only lose 5-10% of the heat. The larger the Ecovat, the lesser the losses. Ecovat is a perfect buffer that gladly can take in every available chaotic kWh it can lay its hands on and convert it into useful thermal heat and next wait patiently for somebody to pick-up that kWh, even months later. Ecovat would solve, not all, but a large part of the energy storage problem.

A few simple calculations. Heat capacity water = 1,163 kWh/m3/K. Heat storage capacity of 1 m3 water between 20-90C = 70 x 1.163 = 81.4 kWh. An average Dutch household uses per year on heating 15,000 kWh, almost all from burning natural gas. This corresponds to an Ecovat storage volume of 185 m3 (volume 6 x 6 x 5 m). For 1000 households, connected to a single large Ecovat, the volume would be 185,000 m3. That’s a sphere with a radius of 35 m or more realistic a cylinder with a dept of 30 m and a surface area of 6167 m2 or 78 x 78 m.

That seems large, however, these figures apply to existing homes that on average are 38 years old, that is were built at a time when concepts like “energy transition” were not yet en vogue. But this is 2019. Dutch law requires that new houses need to be designed with energy conservation in mind and preferably need to be energy neutral. And building technology has meanwhile advanced to the tune that new homes are indeed far more energy efficient.

[] – Ecovat helpt seizoensvariaties in energievraag op te vangen

Ecovat frontman Aris de Groot estimates that the cost per newly built home for participating in an Ecovat storage scheme will amount to ca. 8000 euro and that 40-60 m3 (not the 185 m3 calculated above) of near boiling temperature water are sufficient storage capacity for a heating season. The lifespan of an Ecovat is guaranteed to be at least 50 years (more likely 100 years). That is extremely bearable, not in the least since the Dutch government and banking world are planning “inter-generational loans”, as well as loans attached to a building, not an owner, in order to facilitate the energy transition.

[] – Ecovat energy storage system (54 slides)
[] – Waardecreatie door warmteopslag – Blue Terra Glastuinbouwdag 16 maart 2018

[] – Ecovat plans thermal storage facility for Mijnwater
[] – Eindrapport TKI Energo Project: “Ecovat Total Energy System”
[] – Ecovat wint innovatieprijs voor duurzame energie
[] – Ecovat wint flexprijs


[] – Systeemconsequenties van Ecovat, Kwantificering van kosten voor netverzwaring en piekcentrales (2018)

Renowned Dutch consultancy bureau Berenschot has investigated what the consequences would be for an all-electric national heating system based on heat pumps, especially in the dreaded case of “dark doldrums”, when supply of renewable electricity will go into hibernate mode. According to Berenschot seasonal heat storage systems like Ecovats could provide a solution for grid (peak) overload. Seasonal storage of heat will reduce grid requirements as well back-up power stations.

Read more…

Ecovat bij BNR en TUE

[] – Company site
[] – Energy Day TU/e bespreekt Ecovat-systeem

Ecovat – What’s new?

(Dutch language)

When talking about renewable energy, most people have associations with solar panels and wind turbines. The reality in Europe is though that 50% of the fossil energy budget is spent on space heating. Seasonal storage of heat offer perhaps the largest potential to really save on fossil fuel consumption. The Dutch startup Ecovat provides seasonal storage of heat solutions at a scale of a few hundred households. One 1,000 MWh Ecovat is the storage equivalent of 70,000 Tesla Ppowerwall 2. Ecovat estimates the market potential in the Netherlands of 2,000 vessels or more.

[deepresource] – Ecovat Update
[deepresource] – Ecovat Seasonal Heat Storage
[] – Duurzame Doeners – Het verhaal van Ecovat
[] – Na aardgas komt Ecovat

Ecovat system, suitable for projects in the order of 500 households

Ecovat data sheet: relationship size and storage capacity

XL Ecovat 800 apartments project (realization 2018). Diameter 45m. Concrete elements shipped by boat over adjacent canal.

Ecovat Update

All wonderful these wind turbines and solar panels, the truth is that space heating represents a far greater chunk of the total energy budget than electricity. Seasonal storage of solar-thermal heat could contribute significantly to reduce the fossil fuel footprint. Ecovat is to be seen as a huge thermos, in which it is possible to store water of 90 C and keep 90% or more of the heat contained in the subsurface container for heating purposes during the winter for a few hundreds of houses.

[] – Ecovat needs to be operational in Autumn 2019 in Arnhem
[] – Despite delays, Ecovat-Arnhem operational Autumn 2019
[] – Ecovat ISO 9001 en VCA** certified

“Het Dorp” (The Village) is a community of disabled people that was founded in 1962 after a national 24-hour marathon television broadcasting fund-raiser, eventually amounting to 50 million guilders, an astronomical sum for those days.

[] – Het Dorp (Arnhem)

Het Dorp wil harbor the first large-scale Ecovat storage vessel for space heating in the autumn of 2019.

[] – Ecovat datasheet
[deepresource] – Ecovat Seasonal Heat Storage
[deepresource] – Ecovat Modelling

Ecovat Modelling

[] – Improving an Integer Linear Programming Model of an Ecovat Buffer by Adding Long-Term Planning
[deepresource] – Ecovat Seasonal Heat Storage

Ecovat Seasonal Heat Storage

Storage temperatures up to 93 degrees Celsius and more than 90% storage energy efficiency over 6 months. Scale: 200-1000 houses.

[] – Ecovat company site
[] – Ecovat Smart Thermal Energy Storage
[] – Production line impressions

Read more…

Gravitricity Short Term Energy Storage

Could be used in abandoned mine-shafts.

In theory could be combined with geothermal energy. If you are going to drill a very deep hole of several kilometers anyway, you might as well make it wider and apply a massive concrete or iron “piston” of several tens of meters high and a few decimeter in diameter.

Example: borehole 2 km, diameter 50 cm. Use 10 cm for geothermal, leaving 40 cm. Length piston 30 m. Volume: that’s about 4 m3.
Density concrete: ca. 2.4 ton/m3
Density steel: ca. 8.0 ton/m3
Price steel: $700/ton
We’ll take steel.
Weight of our steel cylinder: 32 ton or $24,000
Energy storage capacity: mgh = 32,000 x 10 x 2,000 J = 640000000 J = 178 kWh
That’s surprisingly little. That’s 4 times the amount of the chemical energy in a car battery.
On an industrial scale we have already battery storage prices of $100/kWh or $17,800 for our 178 kWh “gravitricity”.

Gravitricity is a bad idea and has a 19th century coal mine smell about it.

For seasonal storage of energy, the last remaining missing link to guarantee a total victory of renewable energy, the solution will be either chemical energy storage (like hydrogen) or storage of heat in large water volumes or perhaps CAES.

Mark P. Mills – Hack for the Fossil Fuel Industry

Every now and then you need to lend voice to your opponents and expose their (false) arguments to help make your case. Here we have Mark P. Mills from the Manhattan Institute, trying to make his case, namely that efforts to establish a 100% renewable energy base, as agreed upon in the Paris Accords and spearheaded by Europe, can’t work. Depressingly, this gentleman was named “Energy Writer of the Year” by the American Energy Society. We have linked to three of his articles below.

First he attacks renewable efforts by claiming that “batteries are unsuitable as a storage solution”, which is entirely correct. The point is that nobody worth his energy salt is making that claim. Here is what our renewable betters at the German Fraunhofer institute have to say about a possible 100% renewable energy solution for Germany:

[source] Blueprint for a 100% renewable energy base for Germany

From the Fraunhofer model we learn that in a 100% renewable energy base, most storage comes from hydrogen (“power-to-gas”) and seasonal storage of hot water and that mr Mills’ batteries (as well as pumped hydro-storage) can only play a marginal role. Thermal storage is fed by a mix of solar thermal and electric heat pumps.

Storage capacity:

Category Capacity (TWh)
Thermal 187
Hydrogen 179
Biomass 50
Batteries 9
Pumped hydro 7

The exact numbers will vary for different countries, but for European nations like Holland, Denmark and Britain, this will be the general picture. Sparsely populated mountainous Nordic countries like Canada, Norway and Sweden in contrast will have to rely on hydro-power and have far less (additional) energy storage needs; the existing drainage-basins are the storage.

But these insights are lost om mr Mills, “US-energy-writer-of-the-year-2016”. In his article in “” he refers 21 times to batteries and exactly ZERO to hydrogen. In debating clubs this type of reasoning is known as a straw-man: attacking your opponent by attacking an argument your opponent didn’t make. What mr Mills really wants is frack North-America, ‘Till Kingdom Comes’.

“Frack you, mr Mills!”, we already hear Greta Thunberg saying and we can’t help but agree.

[source] Iconic, but little over-the-top Greta Thunberg

[] – If You Want ‘Renewable Energy,’ Get Ready to Dig
[] – 41 Inconvenient Truths on the “New Energy Economy”
[] – Batteries Cannot Save the Grid or the Planet
[] – Mark P. Mills

[deepresource] – Prejudices From Amateurs Against Wind Energy
(What’s that fascination with the number of “41” anyway with American dissers of renewable energy?)

Below you will find 41 comments (rebuttals) to the 41 thesis mr Mills made in his article “41 Inconvenient Truths on the “New Energy Economy”:

1. Hydrocarbons supply over 80 percent of world energy: If all that were in the form of oil, the barrels would line up from Washington, D.C., to Los Angeles, and that entire line would grow by the height of the Washington Monument every week.

I’m impressed mr Mills. But I have some impressive renewable energy statistics as well:

The yellow area represents the magnitude of annual solar energy reaching earth. It is larger than the cumulative energy contained in all fossil and nuclear energy consumed throughout human history.

An area the size of Bulgaria plastered with solar panels would suffice to replace all energy consumed globally today. It can be done. In the end of the day neither Mill’s stacked barrels of oil, nor our solar chart are decisive. Decisive are they price of energy per kWh, where price includes ALL costs: financial and environmental. In 2019 the situation is such that wind and solar are the cheapest way to produce a ‘raw kWh’, even without susidies, no matter what Mills says. However, the real challenge is to find a cost-effective way to buffer these cheap kWh’s. We are not there yet, but the entire world minus Mark P. Mills are working on it.

Read more…

Photovoltaic Thermal Hybrid Solar Collectors (PVT)

Schematic of a hybrid (PVT) solar collector: 1 – Anti-reflective glass, 2 – EVA-encapsulant, 3 – Solar PV cells, 4 – EVA-encapsulant, 5 – Backsheet (PVF), 6 – Heat exchanger (copper), 7 – Insulation (polyurethane)

Solar panels can convert ca. 20% of the solar radiation into electricity. Solar collectors can convert radiation in warm water or air at much higher efficiencies than those 20%. The tempting idea is to combine these two functions into a single module, a principle known as PVT. There are several construction possibilities: putting a glass cover in front of a black solar panel en pump the heated air away. Disadvantage: one degree Celsius temperature increase of the solar panel decreases the efficiency with about 0,4%. Alternatively, the solar panel can be cooled at the back-side, resulting in less higher temperatures of the panel. In the Summer, with reduced need for warm water, the glass cover could be removed in order to keep temperatures in check.

A little research reveals that in the 2018-2019 the PVT topic is anything but dead. Especially interesting is the prospect of combining PVT with seasonal storage of heat in large volumes of water.

PVT could be a potential solution in areas with high population densities and limited space for separate solar panels and collectors, like in the Netherlands, Flanders or England.

[] – De kansen voor PVT door middel van een analyse volgens Strategic Niche Management (2007)
[] – Evaluation Photovoltaïc-Thermal Solar Panels (PVT, 2008)

[] – Photovoltaic thermal hybrid solar collector (PVT)
[] – Verwarmen zonder gas met het Triple Solar®-systeem
[] – Ecovat PVT module

[] – Systematic testing of hybrid PV-thermal (PVT) solar collectors in steady-state and dynamic outdoor conditions
[] – PVT and seasonal storage: innovative technologies in Spain
[] – Photovoltaic Thermal /Solar (PVT) Collector (PVT) System Based on Fluid Absorber Design: A Review
[] – Numerical investigation of a solar PVT air collector used for preheating the ventilating air in tertiary building under the climatic conditions of Fez, Morocco
[] – New taskforce on PVT collectors to starting its work (2019)
[] – Thermal energy storage: a Spanish start-up achieves high solar fractions
[] – Energy performance analysis of a novel solar PVT loop heat pipe employing a microchannel heat pipe evaporator and a PCM triple heat exchanger
[] – Photovoltaic Thermal (PV/T) Hybrid Solar Panel
[] – PVT: het dak als warmtepompbron
[] – Analysis of a Residential Photovoltaic-Thermal (PVT) System in Two Similar Climate Conditions (2019)

Heat Storage as Key to Seasonal Energy Storage

In NW-Europe, solar and wind energy do even each other out rather neatly as the graph suggests. With a proper mix, the storage requirements are minimized. Yet the picture represents a statistical, long-term average. In reality the electricity supply variations are larger. In comes the Dunkelflaute, a German word for “dark doldrums”:

How to deal with these? The answer comes from the university of Aalborg in Denmark:

[] – Henrik Lund, Renewable heating strategies and their consequences for storage and grid infrastructures comparing a smart grid to a smart energy systems approach

Lund concludes:

“the “smart grid” pathway requires a 2 – 4 times expansion of the electricity grid and significant investments in electricity storage capacities, while the “smart energy systems” pathway can be implemented with relatively few investments in affordable minor expansions of existing grids and storage capacities.”

In short: make use of heat storage with seasonal duration.

An essential fact to consider is that 50% of Europe’s primary energy needs cover heat. While many people associate renewable energy with electricity from wind and solar, the heating sector is the largest in energy land.

Unsurprisingly, this study was picked up by Aris de Groot of Ecovat, specialized in producing seasonal heat storage installations:

The vessel above, with a diameter of 50m, is able to store water at 90C for 6 months and lose less than 10%.

To put it simple: use the November storms to heat up the Ecovat above, using heat pumps and withdraw the heat in January during a Dunkelflaute, so you can use your scarce electricity to keep the lights on.

[] – De kwetsbaarheid van groene stroom – De Dunkelflaute
[deepresource] – Ecovat posts
[] – To realise a renewable energy future a mix of new flexibility options has to be unlocked
[] – Gigantische thermosfles voor energietransitie

Nyrstar – The Next Royal Dutch Shell?

The European Union has decided it wants a 100% renewable energy future and as the saying goes: “He Who Says A Must Say B”, with “A” being a renewable energy base and “B” the required energy storage facilities. This implies giant business opportunities for those companies, that can provide for large-scale energy storage options, options that become a necessity if a society begins to heavily rely on intermittent renewable energy sources solar and wind. Batteries and pumped-hydro can only provide hours worth of storage. What is really required are seasonal storage options, with a size in the order of 40% of annual primary energy consumption, to be able to completely compensate intermittency and waive energy demand management.

Several candidates for seasonal storage exist. First of all the largest share of primary energy consumption is used for space heating. A lot of fossil fuel can be saved if solar heat is stored in large bodies of water or other bulk materials. Excess renewable electricity can be converted in hydrogen and if necessary further converted into other forms of chemical energy that are easier to maintain than hydrogen, like ammonia (NH3), natural gas (CH4).

A relatively unknown possibility is using hydrogen to reduce metal-oxide powder (“reduce” as in: “strip of oxygen”) and turn it into pure metal powder that can be burned again, back to metal-oxide, thus creating a carbon-free closed-loop. Few people realize that metals can burn, a process mundanely known as “rusting”, yet they can, as fine-grained powders, the finer the better:

In contrast to hydrogen, metal powders like iron can be stored, moved around, traded easily at room temperature and ambient pressure for as long as you want, provided you keep moist away. Potentially suitable metal-powder-as-fuel candidates are: lithium (Li), boron (B), magnesium (Mg), aluminum (Al), silicon (Si), iron (Fe), and zinc (Zn).

IF metal-powder can assert itself as an efficient energy storage vehicle for the 21st century, dominated by the EU renewable energy policy and Paris Accords, the sky is the limit for those companies already specialized in reducing metal ores into pure metals. They could become the successors of the Seven Sisters that dominated the 20th century and become the energy companies of the 21st century in that they lay their hands on every renewable kWh and convert it into metal powder.

This possibility has been recognized by Zinc-giant Nyrstar, located near the small town of Budel-Schoot in the South of the Netherlands at the Belgian border, conveniently situated at a run-down, but upgradable “Iron Rhine” railway-line, connecting the Antwerp Harbor and the German industrial Ruhr-valley heartland. This is the rationale behind the recently initiated Metalot energy storage campus, located next to the Nyrstar zinc factory in Budel-Schoot.

[] – Budel

[] – Nyrstar
[] – Recyclable metal fuels for clean and compact zero-carbon power
[deepresource] – How Much Storage is Needed?
[Google Maps] – Nyrstar, Budel-Schoot
[deepresource] – Iron Rhine Revitalized?

Nationaal Actieplan Energieopslag

Energieopslag zal een steeds groter rol gaan spelen in onze energievoorziening. De technologie voor opslag wordt ieder jaar goedkoper, de behoefte aan (snelle) flexibiliteit neemt gestaag toe en de marktmechanismen voor handel in flexibiliteit worden steeds beter.

Kortom, uit een modern energiesysteem is energieopslag niet meer weg te denken.

Toch laat Nederland kansen liggen om de waarde van energieopslag ten volle te benutten voor een betrouwbaar, betaalbaar en duurzaam energiesysteem.

Het Nationaal Actieplan Energieopslag legt de vinger op de zere plekken en geeft suggesties voor het wegnemen van de belemmeringen. Als we door het wegenemen van deze belemmeringen snel een aantrekkelijke thuismarkt creëren, zullen innovatieve technologie- en energiebedrijven hiervan profiteren en de huidige achterstand kunnen omzetten in een voorsprong die wereldwijd verzilverd kan worden!

[] – Nationaal Actieplan Energieopslag (pdf, 32p)

[] – Nederlandse koepelorganisatie energie opslag

Read more…

Prejudices From Amateurs Against Wind Energy


A self-described energy-skeptic & doomer named Alice, who believes that oil can’t be replaced by renewable energy, took the trouble of formulating 41 bold assertions (therefor below in bold), explaining why this would be the case. Every assertion is accompanied by our rebuttals. Judging by the date of the oldest comment, the original blog post was probably written in 2011. A lot has happened since on the wind energy front.

Sneak preview: oil can very well be replaced by 100% renewable energy.

[] – 41 Reasons why wind power can not replace fossil fuels

1. Windmills require petroleum every single step of their life cycle. If they can’t replicate themselves using wind turbine generated electricity, they are not sustainable

Chicken-and-egg story. While it is true that in the initial phase of the energy transition, new wind turbines are by necessity build using fossil fuel, there is no reason why the job can’t be done with energy from wind turbines. In fact, already today most scrap metal is being processed in so-called electric arc furnaces, that run on electricity and thus could be powered by renewable electricity. Furthermore, in a drive to bring down CO2-emission, the Swedish government, among others, is funding efforts to develop steel production without fossil fuels. But even if this would fail, the world gets ever more saturated with iron that can be recycled indefinitely in electric arc furnaces, with ever lower demand for fossil fuel.

Read more…

EROI of Offshore Wind Power [Continued]

Last juli we made a calculation regarding the EROI of wind power, making some assumptions regarding the weight of the wind tower, see link below.

Now we have more accurate data, coming from the implemented Gemini wind farm, consisting of 150 Siemens 4 MW wind turbines. One of these wind turbines weighs in total 1.347 ton max. Annual electricity production Gemini wind farm: 2.6 TWh. That would be 17,333 MWh per turbine annually or 47,487 kWh/turbine/day. We again apply 5555 kWh/ton energy cost in steel production or 7,483 MWh/turbine. Payback time in energy terms: 158 days. Assuming again the worst case scenario of having to transport iron ore from Australia to Europe: 1600 kWh/ton or another 1600 * 1347 = 2,155 MWh which corresponds to 2,155/17,333 = 45 days. Energy payback tower construction + transport iron ore from Australia: 203 days [*]. Assuming an economic life time of 30 years, we arrive at an EROI of 54.

Ignored here is the energy cost of maintenance and installation. And then there is storage.

[*] – Note that after 30 years the energy to create a new turbine from the scrap steel of the old one is less than the energy required to create a wind tower + turbine from iron ore from Australia. There is no transport energy cost other than to bring the tower to a smelter in Europe and in general the energy cost to create steel from scrap metal is (much) lower than from ore. According to Wikipedia the energy required to produce 1 metric ton of steel from scrap metal in an arc furnace is merely 440 kWh/ton (theoretical minimum 300 kWh). It goes without saying that electricity from wind power and arc furnaces are a match made in heaven and can operate on moments when supply of electricity from power is high. In the link “EU Economic Papers” (p14) it is confirmed that the energy intensity of producing 1 ton of steel from ore is a factor of 10 more intensive than producing 1 ton of steel from scrap metal in an arc furnace. If you take this in account than it follows that the EROI of a wind tower produced from the scrap metal of a previous wind tower is in the order of 500-600 [**] rather than the values 54-60 we calculated for the “first generation” wind tower. In other words, the whole EROI discussion of wind energy is obsolete.


[**] EROI 500-600 too optimistic. Here an older piece of information from 2008 concerning a 600 kW onshore wind turbine:

Embodied energy
Onshore wind turbine: 0,6MW, height = 50 m, rotor diameter = 40 m
Production 1900 GJ (embodied energy tower + nacelle)
Installation 495 GJ
Maintenance (20 year) 774 GJ
Total 3169 GJ generated energy
Annual electricity production 5015 GJ
Energy payback time 7-8 maanden
EROI 32 for a very conservative lifetime assumption of 20 years

If we recycle the old turbine we will have a vastly reduced embodied energy for the 2nd generation machine. But we need energy for extraction and transporting the tower back onshore. With maintenance remaining unchanged we arrive at an EROI of 51 instead of 32. But not “500-600”. Note that this is for a very conservative 20 years life time. So far, to our knowledge two windfarms have been decommissioned, one in Denmark and one in The Netherlands, both functioned for 24 years and there is no reason to assume they could not have functioned for many additional years. If lifetime would increase to 40 years you achieve a doubling of EROI (ignoring maintenance). Note that EROI is a logarithmic (see graph at the top), not a linear entity. For all practical purposes an EROI of 50 is not that different from an EROI 500.

The currently most efficient way to store excess renewable electricity is seasonal thermal storage. Think for a country like the Netherlands of thousands of low-tech concrete basins of say 70 m in diameter and 30 m deep, filled with water, that during the Spring and Summer is “charged” with hot water of up to 95 C, using heat pumps, the very same heat pumps installed in homes to heat the homes in the Winter with the storage used as either a direct source or “cold side” once the water temperature begins to drop during the heating season.

[deepresource] – EROI of Offshore Wind
[] – Gemini wind park
[] – Electric arc furnace
[] – EU Economic Papers
[] – Theoretical Minimum Energies To Produce Steel

[] Over the past half century energy intensity of crude steel production fell with 60%

[] Over the coming 23 years energy intensity of steel production is expected to come down even further from 11 to 8 units or 27%.

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