Observing the renewable energy transition from a European perspective

Archive for the category “thermal solar”

DIY Solar Air Heater

Solar air heater DIY-installation, probably dating from ca. 2010. The system can be monitored and controlled per PC or handheld device, via the internet. Solar collectors built from soda cans, controlled by Linux computer. The system fan switches on from the moment 25 C air is available. The system can cool as well, during summer nights. The web link below contains all description necessary to build the system, including software and hardware. Could be built for around 1000,- euro. Location: slightly West of Antwerp, that is 51 degrees North or 2 degrees North of Vancouver (basically the entire US-Canadian border).

Typical flow rate: 700 m3 air/hour
Typical energy yield: 18 kWh in the middle of the winter in 3 hours.
Builder: [linkedin]

P.S. not exactly clear why you would want to use soda cans instead of a simple flat plate construction? The argument seems to be the mediocre heat transfer properties of air, that can be countered by increasing metal-to-air surface area. One wonders if this is worth the effort.

[] – The soda can solar collector

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Warming Up By Cooling Down Your Solar Panels

[] – Company site

Solar Water Heater with Plastic Bottles

Very cheap solution. As said in the comments, the bottles need either to be filled with a black fluid (ink?), or the bottom and backside of the bottles need to be painted black, to absorb most solar radiation.

But, with 20 (5 liters?) bottles, he manages to increase the temperature of another bottle with water (3 liters?) from 28 C to 60 C (in how much time?).

The exact conditions are unclear. It seems to be in-door. Does the radiation come from a big lamp?

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Vertically Mounted Solar Panels

Everyone usually places the solar panels flat on roofs. But researchers at Hanze University of Applied Sciences Groningen have found that erect (vertical) installation of solar panels is much more attractive. A vertically installed solar panel ensures a more even production of electricity over the year. And as a result, a vertical solar panel puts less strain on the energy network. This is apparent from a test set-up that has been extensively tested at EnTranCe | Center of Expertise Energy, part of the Hanze University of Applied Sciences Groningen… The yield of a vertical panel is almost the same in winter and sometimes even higher. In the summer months, the yield is lower and therefore returns less to the energy network. This yield fits better with the consumption pattern of electricity and thus reduces the load on the energy network.

Enough reasons to also promote the arrangement of panels in this way. This is apparent from the research that researchers … of the Hanze University of Applied Sciences Groningen. In the test set-up, both set-ups, vertical and at an angle of 35 degrees to the south, were tested over a period of 8 months.

When we think of installing solar panels, we usually think of solar panels on a pitched roof. Unfortunately, not everyone has a usable roof. Everyone has a usable facade to attach solar panels to. A vertically installed panel produces 70% of the electricity per year compared to a panel installed at an angle of 35 degrees. This means that a panel on the roof at an angle of 35 degrees ultimately yields more, but also has to supply more back to the energy network. This often causes overloading of the network and can be prevented by the vertically arranged panels. (Google Translate)

[] – Oplossing Hanzehogeschool Groningen: Verticaal opgestelde zonnepanelen beter voor energienetwerk

This is exactly what I want to hear, with my “energy wall” ambitions. The 30-year-old garden fence needs to be replaced anyway, so replace it with a robust wooden fence of ca. 1500 euro, next screw 10 matte-black solar panels vertically against the fence and cover these solar panels with 10 double-glazed panels in a click-system, leaving a few cm space between solar and glass panels of 100 x 160 cm each, resulting in a sort of PVT-system, with hot air as medium. Use a ventilator as air pump and create a closed-circuit via a large isolated volume (1 m3?) of gravel or pebbles as heat storage and create a second closed loop through the same storage and living room. With an estimated efficiency of 40-60% and a surface area of 16 m2, that would still amount to 8 kWh/day heat on average during the darkest month December and 1.3-2.5-5.0 times as much in the heating months January/November, February/October and March/September respectively.

Annual solar radiation in the Netherlands.

During the Summer, the glass (or polycarbonate) panels can be removed to avoid overheating, hence the required click-system.

[] – Solar thermal collector
[] – Photovoltaic thermal hybrid solar collector

Note that the yields of vertically mounted solar panels/collectors can be significantly increased by placing horizontal mirrors at the feet of the panels/collectors:

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Passive Solar Heating

I have a SE-facing 10 x 2.2 m = 22 m2 garden fence, not covered by shade from trees, that in principle could be used as an “energy wall”, consisting of PV-panels, with a double-glass cover, to trap solar radiation and convert it in both electricity and warm air. Over the entire year, the vertical energy wall would not yield optimal energy gain, but the point is that you need energy much more in the winter than in the summer, so the vertical position of the fence matches the low position of the sun during the winter.

This post will contain inspirational ideas from already implemented projects and as such updated regularly.

[source] Average solar irradiation in the Netherlands. In December, it is still 70 Watt/m2 during light hours or 55 MJ/m2 = 15.3 kWh/m2 over the entire month or 0.5 kWh/m2 per day. 22 m2 would correspond to 11 kWh/day solar heat or 1 liter gasoline in December, in February that would be 2.5 liter.

The idea is to build a “box” of 10 m x 2.2 m x 10 cm. Since double glass is cheap and durable in the weather, let’s assume that both sides will consist of double glass

[] – price 2 x 10 m x 2.2 m double glass = ca. 932,- euro. The glass back sheet needs to be a black sheet, like blackened triplex or steel wool mesh, or simply painted glass, details to be decided later, after some thermal modelling and calculations. Alternatively I could replace the old fence with a newer solid one that could act as the back sheet, perhaps with an insulation layer over it.

At a later stage, the back sheet can be covered from the inside with solar pv film panels.

[deepresource] – Solar Air Collectors
[deepresource] – Transpired Solar Collector
[deepresource] – DIY Solar Collector For Domestic Heating

[source] 41 m2 garden fence solar, something like this I have in mind.

The number of hours sunshine in Eindhoven increased significantly over the last 40 years, from 1350 to 1800!

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International Attention for Ecovat

It’s wonderful, all these new developments with photo-voltaic solar panels, wind turbines and hydrogen storage, but space heating is still the largest chunk of a national energy budget, at least in Europe. The biggest decarbonization gains can be, and will have to be made, here.

Hence, it is to be greeted that an Austrian periodical pays attention to a promising Dutch startup Ecovat, that offers a solution for seasonal storage of heat in the soil.

[] – Attention for Ecovat in Austrian magazine
[] – AEE – Institut für Nachhaltige Technologien (1988)
[deepresource] – District Heating with Seasonal Storage in Vojens Denmark
[deepresource] – Our Ecovat posts

Ecovat Haalbaarheidsstudie Thermische Opslag Panningen

Het initiatief

In Panningen werkt Ecovat sinds 2018 samen met Peel Energie aan de ontwikkeling van een Warmte | Koude-net. In 2021 hebben de gemeente Peel en Maas en de woningcorporatie Wonen Limburg zich aangesloten bij het initiatief. Het Warmte | Koude-net Panningen biedt een duurzame en betaalbare oplossing voor de lange termijn om huishoudens van het aardgas af te koppelen. Door gebruik te maken van duurzame energiebronnen zoals lokale restwarmte, wind en zon, is er maar weinig tot geen CO2 uitstoot.

Rendabel van het aardgas af

In 2020 is er een haalbaarheidsstudie uitgevoerd door Ecovat. In deze haalbaarheidsstudie zijn de technische en financiële haalbaarheid van een Warmte | Koude-net met een Ecovat seizoensbuffer onderzocht. Uit de studie volgt dat de gebouwde omgeving van Panningen bestaat uit 4.779 woningequivalenten (WEQ) waarvan 3.261 woningen en 1.518 WEQ utiliteit. Voor een groot deel hiervan is het technische en financieel haalbaar om met een projectrendement van 4,6% aan te sluiten op het Warmte | Koude-net, namelijk 3.576 WEQ (2.500 woningen en 1.076 WEQ utiliteit).

[] – Ecovat warmte- en koudesysteem voor Panningen (pdf, 51p)
[] – Nederland bij uitstek geschikt voor energieopslag en omzetten energie

PVT – the Hidden Solar Trump Card

An Amsterdam houseboat owner has installed PVT panels on the deck of his ship, which feeds a heat-pump.

Most people associate solar power with photo-voltaic solar panels, not in the least because of spectacular price decline, with panels of 100 x 160 cm and 300 Watt Wp, costing 100-150 euro.

That wasn’t always the case. The solar revolution started with thermal solar collectors, used for tap water heating, when astronomically priced panels were reserved mostly for space exploration. Increasingly, people begin to understand that both functions can very well be combined. Solar panels are black, meaning that they are energetically “black bodies”, meaning that they absorb almost all solar radiation, go to good old Max Planck for the physics details. That solar radiation can be used both for electricity and heat generation, with a total yield of 1400 Wp per 100 x 160 cm panel.

Modern, commercial solar panels have an efficiency of 20% or more, thermal collectors much higher. Enter “photovoltaic thermal hybrid solar collector” (PVT). PVT panels are more expensive than solar panels [*], but the realization that in the urban environment, space rather than money, is the real limiting factor, PVT could become big, now that the solar revolution is picking up serious momentum, especially in overcrowded and prosperous renewable energy laggard Holland, that enjoyed the ownership of a huge natural gas field, it could milk for decades until prices for renewable energy came down sufficiently to jump on that bandwagon, leaving the real innovation effort to the Danes and Germans, who (deservedly) now own the industries, good for them. (Never mind, we’ll make our renewable energy money from maritime installations and monopiles, North Sea electricity production we can export into the EU and perhaps a share in the future hydrogen trade).

We have collected a few examples of PVT-projects in the Netherlands, captured in video.

[*] – as a rule of thumb, solar collectors cost per m2 about twice as much as solar panels, so for PVT expect a price per m2, three times that of a solar panel.

[] – Black Body
[] – Photovoltaic thermal hybrid solar collector
[deepresource] – Our PVT articles
[] – PVT-producer and installer

PVT-panels applied in a new housing project in Utrecht, this is the easy, happy flow.

Adding solar panels/collectors to new buildings is easy, where solar panels can become the roof itself, eliminating the need for tiles and save cost. The real challenge is to integrate PVT-panels in buildings that weren’t designed for solar, like here in Delft.

In this project it is stressed that PVT-systems can eliminate the need for expensive intrusive underground and thus stationary heat exchangers and instead opt for solar radiation and heat extraction from flowing thin air.

Waalre, Brabant.

Hallelujah-video from a Dutch producer of PVT-systems, QPanel by HRSolar.

PV-panels have 300 Wp, PVT-panels 1400 Wp!

Woning van het Gas af met Warmtepomp en PVT-Panelen

District Heating with Seasonal Storage in Vojens Denmark

In Vojens, in the not too sunny Denmark, the largest storage of seasonal solar heat project in the world is operational since 2016. Denmark is unique in that it has many district heating systems in place, that can be fairly easily adapted to cooperate with large arrays of solar thermal collectors and seasonal storage of the resulting heat in large pits, filled with gravel and water.

Operator: Vojens Fjernvarme
Storage volume: 200,000 m3
Depth storage: 13 m
Circumference: 610 m
Solar collector area: 70,000 m2
Pump capacity: 50 m3/hour
Charging time: 5 months
Location: old gravel pit
Insulation: 60 cm clay and plastic sheet
Number of households: 2,000
Solar heat coverage connected households: 45%
Consequences heating bill: 10-15% less (for 45% no more fuel, just amortization)
CO2-emissions avoided: 6,000 Tonnes/year
Other energy sources: 3xgas engines, 10 MW electric boiler, absorption heat pump, gas boilers
Price pit storage in 2020: 30 €/m3 for storage volume > 100,000 m3
Price storage pit per household: 1,500 €
Installation overhead per household: 100 m3 storage volume and 35 m2 solar thermal collectors

The positive news is that if you can get the thermal solar generation and storage scheme financed, your heating bill actually decreases with 10-15%. This could set in motion an avalanche of projects all over Europe, certainly in countries with more solar radiation than Denmark, that is almost everybody.

In the context of the renewable energy transition, focus is on wind and pv-solar. This is not justified. For an average Dutch household of 2.2 persons, the yearly consumption of energy for heating is 34 GJ. For electricity that is merely 12 GJ. The difference is almost a factor of 3.

[Google Maps] – Vojens district heating

[] – Vojens district heating
[] – Seasonal pit heat storages – Guidelines for materials & construction
[] – South-Jutland stores the sun’s heat in the world’s largest pit heat storage
[] – Seasonal thermal energy storage

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