ECN facts

Solar electricity 1. How does solar electricity work? Types of solar electricity

Solar cells and solar panels

Solar power is a form of solar electricity. It is also referred to as

Solar cells are needed in order to generate electricity directly

photovoltaic solar electricity or PV. Photovoltaic solar electricity

from sunlight. For practical use, solar cells are combined to form

is characterised by the direct conversion of sunlight into electric

a standard solar panel or mounted in a concentrator module.

energy: a voltage and a current. Another, indirect, route is to first

Solar cells are made from semiconductors. The most commonly

generate high-temperature heat, which is then used to produce

used material for commercial solar cells is silicon, in the form

power (Concentrating Solar Power, CSP). PV and CSP are

of a wafer of mono- or multicrystalline material or a thin film of

complementary technologies and can therefore be used to sup-

amorphous or microcrystalline material. Click here for a detailed

plement each other as we move towards a sustainable energy

description of the operation of a crystalline-silicon solar cell.

supply.

New materials Sunlight is also used to generate ‘low-temperature heat’, as in

Gallium arsenide (GaAs) and related semiconductors are usually

the case of solar water heaters or in larger systems. We call this

used for concentrator cells as well as the aerospace industry and

Thermal solar electricity. Finally, laboratories throughout the

solar cars. Nowadays, solar panels based on thin-film copper in-

world are working on a variety of methods to use sunlight for the

dium gallium diselenide (CIGS) and cadmium telluride (CdTe) are

production of fuels, usually referred to as solar fuels. Unlike solar

also available. Solar cells and panels made using other materials,

power and solar heat, solar fuels are still in their infancy.

such as polymers and dyes (‘organic solar cells’) are currently in the laboratory and pilot production phase. In addition to this whole series of existing technologies, researchers are working on a large number of new concepts for solar cells, involving techniques like nanotechnology. The possibilities are virtually endless.

Solar screen in Barcelona. Source: ECN.

ECN Factsheet Solar electricity © 2009

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ECN facts Efficiency An important property of a solar cell, panel or system is the

The world record for solar cell efficiency is 42%, for a stacked

(energy conversion) efficiency. This is the fraction of the energy

cell under concentrated sunlight.

of the incident sunlight that is converted into electric energy. Besides efficiency, stability and llifetime are also very important.

Costs and prices

There is a lot of confusion about efficiency. For example, it is

For large-scale use of solar power, it is important that the

important to make a clear distinction between the (maximum)

generation costs are sufficiently low. The costs per kilowatt-hour

efficiency of small laboratory cells, the (average) efficiency of

(kWh) are determined by:

large commercial solar panels and concentrator modules, and

∙ the turnkey system prices (per watt-peak system power)

the (practical) efficiency of complete systems.

∙ the specific electricity yield (determined mainly by the insolation at the location)

Efficiencies currently being achieved are:

∙ the costs of operation and maintenance

crystalline silicon - laboratory cells - commercial panels thin-film silicon - laboratory cells - commercial panels CIGS - laboratory cells - commercial panels CdTe - laboratory cells - commercial panels polymer solar cells - laboratory cells

∙ the costs of capital (e.g. interest on the loan).

- test panels

up to 25% 12-20%

The system price consists of the price of the panels and the price of the other components, including installation (called the

up to 12% 6-8%

Balance of System, BoS). For the same generation costs, highefficiency panels are allowed to be a bit more expensive than

up to 20% 10-12%

lower-efficiency panels, because the BoS costs are lower (the installation is ‘more compact’).

up to 17% 9-1 1 %

From sun to socket Solar power can be fed directly to the electricity grid, or stored

up to 8%

until it is needed.

2-4%

The latter makes solar power very suitable for remote locations that are not connected to the electricity grid.

Cell and module technologies (‘flat panel’).

Würth Solar

IMEC

Sunconnex

Nuon Helianthos Konarka

Nanosolar

ECN Factsheet Solar electricity © 2009

Commercial: crystalline silicon wafer - monocrystalline (sc-Si) - multicrystalline (mc-Si) - “ribbons” (85% of the 2008 global market) Commercial: thin films - amorphous/microcrystalline silicon - copper-indium-diselenide (CIS) - cadmium telluride (CdTe) - (15% of the 2008 global market) Test production and laboratory: emerging and new technologies - “organic” (polymer and dye) - printed CIS, etc. - super-high efficiency concepts

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ECN facts

Grid-linked system

Short term

converter

PV PV

electricity grid

Solar power is not just an important, or even essential, option for the long term. PV can already make a significant contribution to

user

the realisation of European targets for clean energy in the short Autonomous system

PV

charge controller

storage

term. Depending on the programmes for market development in the EU member states and possible modifications to the electricity grid, according to the European industry association EPIA, 4% to

user

12% of the electricity consumed could be generated from solar power by 2020 compared to 1% at this time (click here for a sum-

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mary of the Strategic Energy Technology (SET) plan for 2020).

Solar power systems.

2. How does solar power help fight climate change?

3. What are the advantages, disadvantages and risks of solar power?

Long term

Advantages and opportunities

Solar power is renewable and sustainable; no hazardous sub-

∙ solar electricity is inexhaustible and available in large quantities

stances are released by the generation of solar power, and the amount of energy needed to build and install the systems is very small compared to what the system generates in its lifetime. The

everywhere on earth; this contributes to the security of supply ∙ the net CO2 emitted from the generation of solar power is very low; this helps to fight climate change

energy payback time currently amounts to one to three years

∙ the costs of solar power are decreasing rapidly and will be level

with a lifespan of 25 years or more, and continues to be redu-

with the consumer prices for conventional power nearly every-

ced. So solar power can replace more polluting forms of energy.

where within ten years; in the long term, solar power will be able

Sunlight is the only renewable source with practically unlimited potential. In principle there is more than enough sunlight available to provide the whole world with electricity and even energy.

to compete with virtually all other types of power ∙ solar power systems are efficient, quiet and clean, and can therefore be applied in densely populated areas (multiple use of space: solar panels on roofs, on noise barriers, against dykes,

Persevere This vast potential is in stark contrast to the limited role played by

above railways, etc.) ∙ solar power systems are modular and can therefore be applied

solar power so far. This is due to the fact that the costs are not

in many different ways and scales: from consumer products

yet low enough and that building and installing huge numbers of

and small autonomous systems, through medium-sized

small and large systems takes time. Even with the impressive recent growth rates, it will take many years before solar power makes a substantial contribution. We simply use incredible

integrated systems to large solar power plants ∙ the development, manufacture and installation of solar power systems offer great business opportunities

amounts of energy, and solar power started from scratch not so long ago. However, solar power is developing very well, and it is therefore a matter of persevering to ensure that solar electricity plays a more prominent role in the generation of renewable energy and the reduction of greenhouse gas emissions in the coming decades.

ECN Factsheet Solar electricity © 2009

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ECN facts

4. What is the public’s perception of solar power? Public support for solar power is high because solar power can be generated safely, cleanly, quietly and reliably, and because solar power systems can be integrated into buildings and other structures. Solar powers also have a (justifiably) high-tech image. In order to maintain public support for widespread use, it is extremely important to control quality in the broadest sense of the word: technical quality as well as aesthetic quality. Systems must work properly and look good, even when they become very affordable, in order to prevent a ‘not on my roof’ syndrome.

5. What is the future of solar power? Expected price decrease Currently, solar power systems are still too expensive. Without financial support, it is not attractive for the average consumer or business to invest in it. However, prices (per watt-peak) are falling quickly, as a result of technological developments combined with upscaling in production and installation. Efficiency is increasing, so that systems are becoming more compact and/or a roof with panels can produce a greater yield. In the last few years, Grain store with solar facade, Germany. Source: Würth Solar.

the price of panels has fallen by over twenty percent with each doubling of the total global turnover. The trend is much the same for complete systems. Prices are expected to decrease at least

Disadvantages and risks

fivefold in the long term.

∙ the market for solar power systems is not yet self-sustaining; market stimulation will be required in the years to come, with developments depending strongly on politics and policy ∙ the supply of sunlight, and thus the generation of solar power, fluctuates; adjustments to the electricity grid and storage will be required for the long term and for large-scale use ∙ some materials used for solar cells are relatively scarce or can be harmful to the environment; ∙ alternatives are needed in order to be able to use solar power sustainably and on an extremely high scale (terawatt)

ECN Factsheet Solar electricity © 2009

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ECN facts

PV Module price experience Curve since 1979 (2009 $/W) 100

PV Module price (2009 $/W)

TF trend silicon trend Thin Films Crystalline silicon

10

Future contribution to the energy supply Although there is a broad consensus on the expected reduction 1 1

10

100

1,000

10,000

100,000

1,000,000

in the price of solar power, opinions vary widely with regard to its

Cumulative Module production (MW)

future contribution to the electricity or energy supply. Estimates Development of solar panel prices. Source: European

on the possible contribution of solar electricity (PV, possibly in

Photovoltaic Industry Association EPIA (2009).

combination with CSP) to the electricity supply in the long term vary from 10% to well over half. If solar power is also converted

Huge, affordable and accepted

into heat and fuel in the long term, it could even meet the bulk of

Between 2010 and 2020, the costs of generating solar power

the global energy demand. Despite the significant differences in

will drop to the same level as the consumer price of conventional

expectations, there is not one leading study in which solar power

power or less. This is called grid parity. The precise moment at

is lacking or plays only a marginal role. Moreover, in recent years,

which grid parity occurs will vary by country as it depends on the

international organisations have systematically revised their ex-

insolation and the local electricity prices. In the decades thereaf-

pectations upwards, stimulated by (sometimes unexpected) rapid

ter, grid parity will also be achieved in terms of wholesale prices

technological developments and price reductions. It is therefore

and possibly even fuel costs. Thus solar electricity will continue

safe to say that the developments in solar electricity play an im-

to grow in the future, to become a huge, affordable and accep-

portant, and possibly even decisive, role in making future global

ted source of energy.

energy use sustainable.

Indicative, rounded figures

1980

Typical turnkey system price (2009 €/Wp)

>30

2009

2020

2030

Long-term potential

Historical and expected future development of solar power. Source: European Photovoltaic

Typical solar power generation costs Northwestern / Southern Europe (2009 €/kWh)

>3 / >2

4

2

(range 2.5~5)

(range 1.5~3)

0.40 / 0.25

0.20 / 0.12

(lower limit 0.15)

(lower limit 0.08)

1

0.5

0.10 / 0.06

0.05 / 0.03

Typical efficiency of commercial flat panel modules

up to 8%

up to 15%

up to 20%

up to 25%

up to 40%

Typical efficiency of commercial concentrator modules

(∼10%)

up to 25%

up to 30%

up to 40%

up to 60%