Heating and cooling Europe with solar from... · installations in Sweden of very large solar district heating systems where large solar thermal collector fields harvest or produce

56 renewable energy focus March/April 2010

Feature article

renewable energy focus March/April 2010 57

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When tAlking About solAr therMAl, it is teMpting to think only

About doMestic hot WAter, And in soMe cAses, spAce heAting,

but solAr therMAl hAs potentiAl for lArger ApplicAtions And

cooling/Air-conditioning. Kari Larsen looks At hoW solAr

cAn heAt And cool europe toWArds 2020.

At the moment, heating and cooling makes up 49% of Europe’s energy

demand – most of which is at temperatures of up to 250°C. Comparatively,

electricity makes up 20% and transport 31%. According to the european

solar Thermal Technology Platform (esTTP), part of the european Tech-

nology Platform on renewable Heating & Cooling (rHC-eTP), today’s

solar thermal technologies are more or less able to cover most of Europe’s

heat and cooling demand – in principle.

By 2030, ESTTP says solar thermal can cover 50% of total heat demand

combined with energy efficiency measures. However, to reach this goal,

new applications need to be developed and deployed. The main applica-

tions would be the active solar building (where all heating and cooling

demand is met by solar), solar renovation, industrial applications up to

250°C, and solar district heating and cooling.

District heating

Around 1% of the European solar thermal market is made up of district

heating systems. Most of the plants cover the heat load in the summer

using diurnal water storage, although some are equipped with seasonal

storage covering a larger part of the load. Over 80% of these installations

have flat-plate collectors.

Denmark, often hailed as a pioneer in the use of renewables, saw an 8000

m2 installation completed in 1995 on the island of Marstal. Combined with

a 2100 m3 water storage tank, it was built to cover up to 15% of the

small island’s annual heating load. The plant has since been extended to

18,300 m2 (12.8 MWth

) with 14,000 m3 of storage.

Xavier Noyon, the new Secretary General of the European Solar

Thermal Industry Federation (ESTIF), tells Renewable Energy Focus: “The

solutions are there – it is not a massive technological gap between

solar systems for single families and for district heating. It is more a

market question than a technology question because there is very

little to develop in terms of technology. It is much more the market

that has to develop further.”

Gerhard Stryi-Hipp, President of RHC-ETP and part of ESTTP, says solar

thermal district heating is still relatively expensive compared to heating

from oil and gas, and therefore this market segment will not grow as fast

as other potential solar thermal applications. “But district heating and

utility scale district heating is a very promising future application.”

Heating and cooling Europe with solar

A block of municipal housing in Budapest, Hungary, with 886 dwellings has been fitted with 15,00 m2 of TiSUN solar collectors to produce hot water. (Image courtesy of TiSUN)

56 renewable energy focus March/April 2010 renewable energy focus March/April 2010 57

Solar/Thermal

Process heat

One area where both ESTTP and ESTIF predict that solar thermal has

great potential, is for industrial process heat in applications up to 250°C.

However, this is still very much in its infancy. In 2008, less than 100 oper-

ating solar thermal systems for process were in used with a total capacity

of around 24 MWth

.

Industries that could make use of solar thermal for their process heat

demand include food; wine and beverages; transport equipment;

machinery; textiles; and the pulp and paper sector.

One obstacle, however, is the prohibitive upfront cost, with many investors

looking for short return-on-investment times – something solar thermal

cannot yet meet. This combined with a less impressive track record and

industry’s often discounted contracts for oil or gas supplies, add to the

barriers that need to be overcome before industry can adopt solar thermal.

Domestic hot water and heating

Stryi-Hipp says: “Space heating is very popular in Germany, Austria and Swit-

zerland, and also partly in France. In Germany and Austria, the share of the

market for space heating or combined systems is about 50% or more. In

other regions of Europe – in Southern Europe – like Spain, Italy, or Greece,

domestic hot water systems are prominent and space heating is less popular.

“With domestic hot water systems, you can cover about 60-70% of the

energy demand for domestic hot water annually. For space heating or

combined systems which support space heating in an efficient building,

you can cover 20-30% of the overall heat demand with a solar thermal

system,” he adds.

Noyon adds that in addition to pure solar thermal systems of hot water

and/or heating, another trend is to combine solar thermal with current or

renovated heating systems – so combining solar thermal with for example

a fossil fuel-based boiler.

These systems could run entirely on solar when weather conditions allow

it. “In nearly all climates in Europe – perhaps except the really northern

parts – there is always somewhere you could completely switch off your

heating system when the [solar thermal] system meets all hot water and

heating demand. So you can optimise the use of the other [fossil fuel]

source,” Noyon tells Renewable Energy Focus.

Combination systems could also use other forms of renewable energy

instead of fossil fuel, for example heat pumps, biomass, and condensa-

tion heaters. “Solar thermal has a competitive advantage because it can

be combined with any other source, and if you only buy the solar thermal

part, the investment is not so big.”

Noyon predicts that in the future, large buildings – for example, large

hotel complexes or resorts – could use solar thermal to cool the air, heat

the swimming pool, and provide space heating when needed.

Cooling and air-conditioning

According to ESTTP figures, around 250 solar air-conditioning systems

were installed in Europe by 2007. Solar cooling is divided in two main

types: open cooling cycles and closed cycle machines. In open cycles,

a sorptive component is in direct contact with environmental air, and

is able to dehumidify the air. Closed cycle machines have a refrigerant

undergoing a closed thermodynamic process.

According to ESTTP, heat driven cooling is still new and “relatively unex-

plored technology.” It therefore has scope to reduce costs and increase

performance. Solar cooling also faces many of the same obstacles as solar

heating: high investment cost, the question of building integration, lack

of design guidelines and tools, and awareness.

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Solar

/Thermal

Upcoming events—09_Diary/IndexSolar cooling in cafeteria kitchen Fraunhofer ise has had a solar-powered adsorption chiller assisted by earth probes in its cafeteria kitchen since 2007. the ACS05 adsorp-tion unit from sorTech aG has a cooling power of 5.5 kW. in winter, its operational mode is reversed to provide heat.

three 80 m deep earth probes serve as heat sinks for the adsorption unit, and the system’s driving heat is powered by a 2 m2 flat collector field on the roof of the institute.

the adsorption chiller uses water at low pressure (about 10 mbar).

SOLID systems in Graz, Austria

A sOLiD solar district heating system in graz, Austria, with a collector area of 6903 m2 was commissioned in 2007/2008 and completed in 2009. the collectors were mounted on five separate industrial roof areas.

the high-temperature collectors yield approximately 2.2 gWh annually, and the system’s output can be followed in real-time at http://tinyurl.com/yfh6ebb

solid has also installed solar collectors covering 2417 m2 on the roofs of 6 buildings at the Berlinerring housing estate in graz. the solar system provides hot water for 756 residential units, and is backed-up by a 60 m3 heat storage tank.

the annual yield is approximately 1 gWh.

Solar plant combined with district heating, 10,000 m2, Kungälv Sweden. (Image courtesy of ESTIF)


Solar/Thermal


Stryi-Hipp says: “We’re only in the starting phase of the first pilot and

demonstration phase in Europe. … We have to reduce the size of the

absorption and adsorption chillers, make it more compact and reduce

the investment cost.”

ESTIF’s Noyon says solar cooling is becoming more and more popular.

“Solar cooling is extremely interesting because one of the main problems

of solar thermal is that you get less production possibility at the time

of the year you would need it most. Let’s say in the average European

climate, you wouldn’t be able to cover your heat demand with solar at

the time of the year you need it most [in winter], and when you need it

less in the summer, that’s when your production capacity is at its peak.”

Solar cooling would allow the exploitation of the summer sun’s energy

capacity. As with district heating, the technology is there, “but the market

is developing slowly,” Noyon says. That said, ESTIF member ClimateWell

aB of Sweden, have been reported as saying they sell a solar cooling

system a day.

Storage

But what if you want heating and/or cooling when the sun is not shining?

Storage for one to two weeks is already widely used, but seasonal storage –

i.e. storing heat from the summer sun to use in winter – is still in its infancy.

In order for solar thermal to meet all of space heating and hot water

demands in domestic housing, storage development is crucial, according

to ESTTP. The most common storage medium is water; but it has low heat

capacity, and therefore requires large space.

Stryi-Hipp says the key to storage is to increase the heat density. “You

need seasonal storage where you are storing the heat from summertime

into wintertime. This is possible today with water storage, but water

storage has a high volume – typically you have a volume of more than

about 10 m3 for a solar fraction of perhaps 70%. The goal is to reduce the

size of the storage by storing the same amount of heat energy.”

One technology could be phase-change materials (PCM), which can be

used to store energy at lower temperature levels. The second technology

is chemical storage where it is possible to store a higher amount of

energy at the same volume. “There will be several R&D projects in the

coming years to elaborate possibilities to improve the heat density in that

storage,” Stryi-Hipp says.

Storage also enables the use of solar thermal in regions such as Northern

Europe, which has less sunshine in winter. “Already in the 1990s, we saw

installations in Sweden of very large solar district heating systems where

large solar thermal collector fields harvest or produce heat. This heat is

stored in very large seasonal storage in the ground,” Stryi-Hipp explains.

One solar heating and cooling company that is looking into the storage

question, is Austrian solar installation and Design (sOLiD). CEO Dr

Christian Holter tells Renewable Energy Focus: “There are concepts that use

different combinations of salt and water. … The really highly-concentrated

and really low concentrated solutions have different energy content.

“It might turn out that for different applications you need to use different

concepts. Latent heat is really efficient in a small band of temperature

change, and the situation of the other concept is you can have long-term

storage without much loss. But they are two different concepts that might

end up in different applications,” he adds.

Further research

ESTTP says research challenges to reach the stage where solar thermal

can meet 50% of total heat demand in Europe in 2030, include long-

term efficient storage. Other developments needed are new materials

for solar systems, improvements in solar cooling, and high temperature

solar collectors. “Today, perhaps 0.1-0.2% of the overall heat demand is

covered by solar thermal, so we have a lot to do to increase it to 50%,”

Stryi-Hipp says.

Solar collectors can still see significant improvements – especially in terms

of cost reductions and designs. But ESTTP says low temperature collectors

used on buildings are already “very efficient.”

Stryi-Hipp does not believe major improvements in efficiency on the

collector side will be possible, but that research is needed on how to

integrate solar thermal better into the building envelope. Alternative

concepts for collectors such as air collectors, solar thermal photovoltaics

(PvT), and collectors for higher temperatures will also be needed.

ESTTP’s vision for solar thermal in 2030 includes the following key elements:

■ establish the Active Solar Building as a standard for new buildings by 2030 – active solar buildings cover 100% of their heating and cooling demand with solar energy;

■ establish the Active Solar Renovation as a standard for the refur-bishment of existing buildings by 2030 – active solar renovated buildings are heated and cooled by at least 50% with solar thermal energy;

■ satisfy with solar thermal energy a substantial share of the industrial process heat demand up to 250°c, including heating and cooling, as well as desalination and water treatment and a wide range of other high-potential processes; and

■ Achieve a broad use of solar energy in existing and future district heating and cooling networks, where it is particularly cost effective.

Air collectors for cooling installation in Freiburg, Germany


Solar/Thermal

SOLID’s Holter says: “There’s definitely still potential on the collector side.”

Although, he adds: “However, the more critical point is to prove the system

concept, because on the panel you may be looking at a 1-3% gain in effi-

ciency, but if you have some system achievements that do not turn out prop-

erly, you can easily lose 20% of the gain.”

Policy

So what policies and incentives affect, and drive, solar heating and cooling?

ESTIF’s Noyon says the European energy efficiency policy, which is important

for the building sector in general, will be important for solar thermal heating

and cooling as well. But he points out that only having energy efficiency poli-

cies for new build is not doing enough to meet the EU’s 2020 targets. “What

about the rest of the building stock?” Noyon asks.

Stryi-Hipp says: “We need political support to raise awareness with the

customers and the people who could invest in solar thermal systems. We need

incentives and some support programmes in order to make it attractive … On

the other side, we need more R&D activity in order to develop the technolo-

gies further to be able to enter [more] market segments.”

Last year, the EU announced the Renewable Energy Directive, and for the first

time, renewable heating and cooling was mentioned in a directive, something

Stryi-Hipp calls “a great success for the heating and cooling sector.”

At the moment, there are mainly two ways in which solar thermal heating and

cooling is supported in Europe, and that is through incentives or tax reduc-

tions, which is used in Germany and France respectively; or having laws and

obligations to use solar thermal in new buildings or renovations, which is the

case in Spain and partially in Germany.

“The incentives policy differs a lot from country to country in Europe, but most

of the countries do have incentive programmes or obligations – which is a

good basis [for solar thermal]. But what we also see is it needs continuation,

continuous support, and awareness programmes. … We also need installers –

they have to be trained,” Stryi-Hipp says.

“The second point is that on the European level – and more and more on

national levels – there is an increase in building standards and increased

requirements regarding building standards. What we expect over the coming

years is that investors in the building sector will have to use solar thermal

energy in order to fulfil those requirements,” he adds.

The market

With some incentives already in place, where is the solar heating and cooling

market at today?

June 9–11, 2010

The World´s Largest

Exhibition for the Solar Industry

New Munich Trade Fair Centre

Germany

1.500 Exhibitors

130.000 m2 Exhibition Area

60.000+ Visitors

www.intersolar.de

AZIS2010_86x258 en:Layout 1 09.03.10 13:00 Seite 1

“the solutions are there – it is not a

massive technological gap between

solar systems for single families and

for district heating…” – Xavier Noyon, Secretary General of the European Solar Thermal Industry Federation (ESTIF)


Solar/Thermal


Germany was the biggest solar thermal market in 2008 with 1.5 GWth

(2.1 mil m2 of collector area), according to ESTIF. Spain was second with

988 MWth

(1.4 million m2), followed by Italy: 295 MWth

(421,000 m2), France:

272 MWth

(388,000 m2), and Austria: 243 MWth

(ca. 350,000 m2).

In September 2009 ESTIF said solar thermal could make up 6.3% of the EU’s

20% renewable energy target, representing an annual sector growth rate of

26%. And by 2050, solar thermal has the potential to cover 47% of the EU

low-temperature heat demand.

According to ESTTP, a global market size of 160 GWth

(250 million m2) per year

can be predicted by 2020, based on an annual growth rate of 20%.

ESTIF’s Noyon says that in the first 11 months of 2009, 3.9 million m2 of solar

collectors were sold in Europe – of which approximately 80% were flat plate

collectors and 20% vacuum collectors.

The recession – a geographical shift

2009 was a very hard year to assess due to the recession. However,

ESTIF’s Noyon says: “Investment in solar thermal has not been completely

stopped following the problems of 2009 and the recession. The

production capacity in Europe is still growing, but the trend we see is

that investment has been relayed also a lot to outside of Europe. Some of

the manufacturers in the European market are now trying to compensate

for the fact that the European market is perhaps not growing as fast as

they would have expected.”

Outside of Europe, investment has mainly been in America and India. “The

Chinese market is a bit different because there are mainly Chinese manu-

facturers – they have a much larger solar thermal industry, but it’s much

harder to penetrate there,” Noyon adds.

Markets particularly hard hit by the recession include Germany, Austria,

Spain, France and Italy. “Germany suffered a lot – an estimated 30%

decrease. Markets like Spain, France and Italy have also suffered – and

suffered at a time when they were really taking off, starting to grow

really fast.”

Hit by building sector collapse

Spain’s solar thermal market was hit hard despite a solar obligation that

all new buildings must include renewables – and this is because of the

near collapse in the new building market that came with the reces-

sion. Noyon says: “Our growth is very much linked to the growth of the

building sector.”

Countries like Poland, Hungary and Slovakia are still growing, however.

“Probably because they have not been subject to the trend like [we’ve

seen] in countries like France and Spain, where it’s very much linked to

the building sector,” Noyon says. “Also, the market level is low – they’re

going from such a low figure.”

Investors

According to Noyon, investment in solar thermal has come mainly from

companies who are not only solar thermal manufacturers alone, but large

classical heating companies such as Bosch.

Utilities, on the other hand, have not shown much interest in solar heating

and cooling. “Solar thermal is not really on top of their agenda,” Noyon says.

This is partially due to strong feed-in tariffs for solar photovoltaics (PV). “In

some countries, for example France, where electricity cost is so low, a lot

of people will have heating systems powered by electricity. So in the short

term, they would have a much better return on investment by installing PV

on the roof, and selling the electricity for a subsidised price,” he says.

Solar thermal collectors and applications:

Low temperature applications (<80°C): these are the most common collectors usually deployed for domestic hot water and space heating. glazed flat plate (85% of european market) and vacuum tube collectors (10-15% of european market) dominate. for very low temperature applications such as swimming pool heating, unglazed collectors and fully cpc stationary concentrators are sometimes used.

With the introduction of anti-reflection coatings, efficiency improvements of around 5% have been seen for flat plate collectors. however, the increased efficiency can lead to higher stagnation temperatures of up to 250°c, whereas the output temperature remains at around 80°c.

Vacuum tube collectors are in general more efficient than flat plate, especially at higher temperatures. however, stagnation temperatures can be a problem here as well.

Medium temperature applications (80-250°C): this category includes thermally driven cooling technologies, process heat (including various industrial processes), desalination and water treatment.

High temperature applications (>250°C): these high concentration technologies are mainly used to produce electricity through thermal cycles such as parabolic troughs, fresnel concepts, solar towers and paraboloids.

Types of storage

sensible: uses the heat capacity of a material. the majority of systems on the market use water sensible heat storage. other mate-rials are concrete, molten salt or pressurised liquid water;

Latent: thermal heat energy is stored during the phase change (melting or evaporation) of a material. this is typically more compact than using water. for medium temperatures, nitrate salts are used;

sorption: heat is stored in materials using water vapour taken up by a sorption material. the material can be solid (adsorption) or liquid (absorption). sorption heat storage densities can be more than four times that of sensible heat storage in water;

Thermochemical: the heat is stored in endothermic chemical reactions. Materials currently under investigation are all salts that can exist in anhydrous and hydrated form. thermochemical systems can store both low and medium temperature heat.

According to esttp, heat driven cooling

is still new and “relatively unexplored

technology.”


Solar/Thermal

Noyon envisages a future cooperation with utilities, however, where

customers would be offered a new type of contract where the utility

would finance the initial investment cost and the customers paying

back through the energy savings they make by not using conventional

sources of power.

Cost and payback times

One question often asked by investors, is ‘what will it cost, and when

will we get a return on our investment?’ Stryi-Hipp says these factors

depend on policy decisions and energy prices going forward.

The cost for solar thermal is usually concentrated at the installation

phase with low maintenance costs from there on. It is possible to

simply divide the total sum on the amount expected to be produced

by the system over its lifetime and compare that with energy prices.

“But since we don’t know how the oil and gas prices will develop, we

can only make assumptions,” Stryi-Hipp says. However, solar thermal

has the advantage that the cost stays the same over the lifetime of

the system.

“If you assume an oil price and gas price having a continuous increase

over the next 20 years of for example, 5% annually – we’ve seen much

more over the last 10 years, but if you calculate with 5% – then solar

thermal systems are already cost competitive,” Stryi-Hipp says.

According to Holter at SOLID, solar thermal is already a competitive

technology if done right. But as Stryi-Hipp points out – it depends on

assumptions about future energy prices.

“Some say: ‘I expect fossil fuels to stay at the same price level for the

next 20 years’ – and that’s a really tough sell. But some say: ‘I expect

oil to increase by almost 10-20% every year’ – then the deal is almost

done,” Holter says. “The problem, I would say, is the high initial cost,

because you have to ask people to put energy costs for the next 5-12

years on the table in one go. This is definitely a hurdle.”

According to ESTTP estimations, solar domestic hot water is often

already cost-competitive with fossil-fuel based solutions over the life-

time of the solar thermal system – if positive boundary conditions are

in place. The Technology Platform believes that by 2030, solar thermal

costs could come down by 60% through technological progress and

economies of scale.

Over the last 10 years, for every 50% increase in the total installed

capacity of solar water heaters, an approximate 20% reduction has been

observed in investment costs (in Europe), ESTTP says. This does depend,

however, on geographical location and local policies.

THE RENEWABLES SHOW IN THE ENERGY CITY – ABERDEEN 19/20 MAY 2010

All-Energy 2010 – the UK’s largest renewable energy exhibition and conference – looks forward to welcoming you as anexhibitor or visitor. 5,500 from 60 countries attended All-Energy ’09 with its 380+ exhibiting companies from 14 countries andmore than 250 conference speakers. The major exhibition features technology across the full range of renewable energy devices;and the free-to-attend conference looks at issues and challenges facing the industry and at renewable energy sources frommulti-million pound offshore projects to microgeneration. Networking opportunities abound.

Be there!See regularly updated information at: www.all-energy.co.uk

AE2010_0028 REF:Layout 1 18/12/09 14:02 Page 1

Click through ■ Solar cooling market ripe – http://tinyurl.com/yzgkn3q ■ Fraunhofer expands solar thermal testing – http://tinyurl.com/

yzjghfl ■ US Senate considers legislation for 10m solar roofs – http://

tinyurl.com/yhlzcgm ■ California PUC introduces solar water heating incentives –

http://tinyurl.com/ykmmqks

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Heating and cooling Europe with solar from... · installations in Sweden of very large solar district heating systems where large solar thermal collector fields harvest or produce