Non-carbon energy source: Solar Power
What is Solar Energy?
Solar energy is, broadly speaking, the radiant energy emitted by the Sun . Humans are able to capture this energy in two unique ways: Passive Solar Energy can be exploited through architectural design, as by positioning windows to allow sunlight to enter and help heat a space. Active solar energy involves the conversion of sunlight to electrical energy, achieved primarily through Solar Photovoltaics (PV) and Concentrated Solar Power (CSP).
What makes it a viable energy source?
The need for cleaner forms of energy production is well documented. Hydrocarbons are recognised as a finite resource where globally, reserves are being rapidly depleted. As the 'Peak Oil' crisis approaches, countries have responded to the pressures by developing renewable energy sources. Fossil fuels are also contributing to the atmospheric concentrations of greenhouse gases which cause anthropogenic climate change. There is worldwide recognition that climate change is a significant threat, and that reducing the carbon signature of energy production is a vital step in addressing climate change.
“Energy systems will take decades to change but we need to start now with major drives to improve energy efficiency and a determined transition to a low-carbon energy system. This means lowering the carbon intensity of electricity;, using renewables such as solar and wind, as well as carbon capture and storage and nuclear power.” Dr Nilay Shah - Director of the Centre for Process Systems Engineering, Imperial College London 
Solar energy’s potential is off the chart, and it is for this reason that so much hype surrounds the development and application of solar technology. The energy within the sunlight striking Earth for just 40 minutes is equivalent to global energy consumption for a year – and if we can learn to harness it efficiently the result will be an energy source which is clean, renewable and inexhaustable . The costs of solar energy have been falling rapidly and are entering a new era of competitiveness; now at the point where Concentrated Solar Power (CSP) and Solar Photovoltaics (PV) are competitive against oil-fueled electricity generation in certain areas .
In most markets, solar electricity is not yet able to compete with traditional forms of power (i.e. fossil fuels) without specific incentives, however these incentives are becoming more widespread.
History of Solar Energy
Humans have been harnessing the power of the sun for a significant amount of time. Passive solar energy has been used for building designs as a means of heating for thousands of years . Active solar technology, however, converts solar energy to another form of energy using electrical or mechanical equipment. For the purpose of this wiki page the use of the term solar energy will be referring to active solar energy. The most prevalent technology used for solar energy is Photovoltaics (PV). A brief timeline of some of the historically significant developments in PV is listed below.
- 1839 – French scientist Edmund Becquerel discovers the “photovoltaic effect”. Becquerel found that when specific materials were exposed to light, they would produce small amounts of electricity .
- 1883 – The first solid-state PV cell was built by Charles Fritts using the elements selenium and gold . The solar cell had an efficiency of around 1%.
- 1887 – Heinrich Hertz found that electrons are emitted from solids, liquids, and gases when absorbing energy from light. The process is known as the “Photoelectric effect” and was proved by Albert Einstein in 1905, earning him a Nobel Prize .
- 1954 – The first modern, or practical, solar cell using silicon is developed by Bell Laboratories . The silicon solar cell had an efficiency of about 6%.
- 1954-1960 – Hoffman Electronics Corporation improves solar cell efficiencies to around 14%. Hoffman solar cells were used for the first time to power a satellite (Vanguard I) in 1958 , which was also the first commercial application of silicon PV cells.
- 1960-1980s – The efficiencies of PV cells during this time period did not improve very much. The price of PV changed considerably however. The production price of PV cells fell from about $250 per watt in the early 1960s to $10 per watt in 1973 (Perlin 1999).
- 1983 – PV energy produced worldwide is around 21.3 megawatts, and PV sales are in excess of $250 million (Perlin 1999).
- 1994 – The first solar cell to exceed 30% efficiency is created by the National Renewable Energy Laboratory in the U.S. .
- 1999 – PV energy produced worldwide reaches 1,000 megawatts (Perlin 1999).
Passive Solar Energy
Passive solar is the practice of using building design to store and use heat from the sun without transforming the heat into any sort of power . Civilisations have been taking advantage of simple passive solar techniques over human history such as orienting dwellings to take advantage of the passing sun , however since the 1970 more research has been put into the subject and there are much more advanced techniques. Constructing walls out of material with a high specific heat capacity so that it captures heat and releasers it over a long period of time, this can be advanced upon with a Trombe Wall which is covered by glass held about 6-10cm above the surface of a thermal mass material. The glass allows heat to enter as short wave radiation but stops it from exiting through long wave radiation thereby increasing the efficiency of the thermal mass .
The light produced by the sun is made up of photons, packages of light that can be absorbed by objects. The photons can then excite the objects at the molecular level causing them to emit electrons. This is the photoelectric effect and the principle behind solar photovoltaic panels. Current efficiencies for industrially produced solar panels are 15-18% while research examples have reached up to 25% .
To reach competitive price per watt levels with current non-renewable energy sources PV panels will need to become at least 30% efficient. Globally Germany and Spain have the most energy produced through solar PV, currently 5% of the German grid. The majority of these PV panels are installed on home rooftops, only 1/5 of German PV electricity is from large scale 'solar farms'. The limiting factors of solar PV are that at large scales it takes up a large amount of space and are time consuming and technically difficult to produce .
Concentrated Solar Power (CSP).
Mirrors in one of the four configurations concentrate the light on to a central point or pipe that absorbs and/or transports the heat and uses this to generate steam which drives a generator . The advantage of this system is that the thermal energy produced can be stored to use at a later time. The peak time for power consumption is 5pm, generally there is not enough sunlight to produce the heat required to create power. However because the heat can be stored CSP systems can generate power almost 24 hours after heat intake . Currently price per watt of CPS electricity is 4-8 USD however advances in technology and decreases in production cost will bring this value down moving forward . CSP electricity production also scales well with the size of the installation (the bigger the plant the more efficient it will be) and we are seeing larger and larger CSP plants being planned as the technology becomes more viable .
Trends & Indicators at a Global Scale
There exist well documented indicators relating to solar energy production from both private and public sources. Annual solar installations and Cumulative solar installations (measured in MWs) are the most widely used indicator of the growth of solar power generation, both of which have been increasing rapidly since 2008. Other widely used indicators include:
1.) Installed cost ($/kW)
2.) Market share of solar energy (%)
3.) Net change in energy production over a time period (%)
Over the period 2000‐12, Solar PV was the fastest‐growing renewable power technology worldwide . PV production in 2012 declined 2 percent from 2011, the first annual drop on record, however this contraction is forecast to be short-lived as demand continues to rise. Solar power installations are growing more than 40 percent annually, and falling PV prices are making solar power more affordable.
Going solar is becoming increasingly attractive in developing countries such as India and Bangladesh due to notoriously frequent blackouts and climbing grid power prices; not to mention that solar is now cheaper than diesel for electricity.
The feed-in tariff (FIT), which enabled Germany and Italy to amass their world leading production of solar energy, guarantees renewable energy generators a long-term purchase price for the electricity they supply to the grid. As these markets mature and solar system costs decline these FIT incentives are being reduced. However this strategy is becoming more widely adopted to encourage residential PV installations, and more than 70 countries now use some form of FIT.
Another notable global trend in the production of solar energy is the rise of the mega-project. Only a few years ago, the 10 largest solar farms were between 30 and 60 megawatts. Now parks of 100 megawatts or more are becoming commonplace. Arizona’s Agua Caliente PV project became the world’s largest at 250 megawatts when its fourth phase finished construction in 2012. Developers have announced a 475-megawatt PV farm in Nagasaki, Japan, due in 2016, while several projects between 500 and 3,000 megawatts are under development in California.
PV installation is on target to reach a record of 35,000 megawatts in 2013. Even with the possibility that Europe’s annual installations will fall below 10,000 megawatts over the next few years, China, Japan, and the United States, along with the growing number of “newcomer” PV countries, will more than pick up the slack. The International Energy Agency (IEA) conservatively estimates that world PV capacity will more than triple by 2018 to 308,000 megawatts — at peak power this represents the equivalent of 300 large nuclear plants . The most extreme IEA forecast predicts that solar energy could provide up to one-third of the world’s final energy demand after 2060 .
Regional Scale Trends - United States
The vast landmass available to the United States makes it ideally suited to solar power generation. In 2012, the ‘National Renewable Energy Laboratory’ estimated that the technically available solar potential of the United States sat at 400,000Twh/year – over 100 times the entire 2011 energy budget. The application of solar power however remains limited, with just 0.14% of the national electricity budget being supplied through solar means in the 12 months through May 2013 . The application is most noticeably restricted by the costs involved with the application of Photovoltaic (PV) Panels to residential properties, and despite advances in technology, solar panels remain almost prohibitively expensive without federal subsidies. As a result, small-scale solar rooftop installation costs in the U.S. remain higher than a number of other similarly-developed markets in other countries .
Residential Scale Initiatives
While the cost of solar hardware i.e. panels, has come down 80 percent since 2008, the biggest hurdle to affordable solar energy remains the soft costs; including permitting, zoning, and hooking a solar system up to the power grid. On average local permitting and inspection processes add more than $2,500 to the total cost of a solar energy system . The Energy Departments SunShot Initiative works to aggressively drive down these soft costs – making it faster and cheaper for families and businesses to go solar. SunShot is the Department of Energy’s effort to work with industry, government and researchers to bring the price of solar power down to that of conventional power by 2020. The DoE currently invests about $300 million per year in solar energy technologies . At one end of this spectrum, the Energy Department selected small businesses to turn revolutionary ideas into proof-of-concept demonstrations through the SunShot Incubator program. In the sixth round of this successful program, the selected awardees will tackle the hidden costs that drive up the price of owning and installing a photovoltaic (PV) system. At the other end of the spectrum, the Energy Department is launching America’s Most Affordable Rooftop Solar for installers across the nation to compete for a total of $10 million in cash prizes. This race to the top encourages companies to evolve their business models so that home owners and businesses can install residential-scale rooftop solar systems at an average cost of $2 per watt (W) .
Advocates say that solar is, at long last, ready to move into the mainstream. Photovoltaic panel prices are falling, low-cost financing for installing rooftop solar is available, and Federal and state government incentives remain generous. Solar panels installed across the US now have enough power capacity to power up to about 1.5 million average US homes. That’s approximately enough to power Philadelphia or Phoenix, the nation’s 5th and 6th largest cities. In 2013 about 4.4 GW of solar PV power capacity are projected to come online, a value about 30% higher than in 2012. This is largely due to solar panel costs having dropped 80% in the 5 years since 2008. These costs are partly down due to technological and manufacturing advancements. However the main driver of the reduction in installed solar panel costs is likely just economies of scale, with an increasing demand allowing the production costs to be driven downwards.
Utility Scale Initiatives
While the major focus of the SunShot initative is to drive down the cost of PV applications at the residential scale, they also recognize the huge potential for large scale, industrial solar projects in the countries southwest . Current projections suggest that well designed solar projects in the sun rich southwest could provide up to one third of the nations electricity needs. Since 2010, the Bureau of Land Management (BLM) has approved 25 utility-scale solar energy projects, including connected-action projects that include electric transmission support authorizations, with a total approved capacity of over 8,000 megawatts of clean, renewable energy — enough energy to power roughly 2.5 million homes. In addition, the BLM currently has some 70 pending solar energy applications . In 2012 the BLM also approved ‘The Western Solar Plan’, which provides a blueprint for utility-scale solar energy permitting in Arizona, California, Colorado, Nevada, New Mexico and Utah. This plan established solar energy zones with access to existing or planned transmission, incentives for development within those zones, and a process through which to consider additional zones and solar projects. The Western Solar Plan established an initial set of 17 Solar Energy Zones, totalling about 285,000 acres of public lands that serve as priority areas for commercial-scale solar development, with the potential for additional zones through ongoing and future regional planning processes. If fully built out, projects in the designated areas could produce as much as 27,000 megawatts of solar energy, enough to power approximately 8 million homes. The program also keeps the door open, on a case-by-case basis, for the possibility of carefully sited solar projects outside SEZs on about 19 million acres in "variance" areas .
Regional Scale Trends - European Union
Europe is a key contributor in the solar PV market and global cumulative capacity, contributing approximately 70% of the total cumulated installations in 2011 . Germany alone accounts for a significant proportion (34.5 GW) of the cumulated installed PV capacity (around 64GWp by the end of 2011) worldwide . Although the majority of Germany has poor irradiation over the majority of its landmass, it has still managed to become the top PV installer worldwide.
In the EU, renewable power generation has steadily increased to 25.1% between 1991 and 2000, however even more impressive is Germany’s growth, which grew a staggering 141.5% . This escalating generation capacity is thought to be the result of the federal governments renewable energy policies, which have proven effective in setting Germany on the path to becoming one of the worlds most energy-efficient countries in the world . Their policy’s are based on creating a cost-effective market-based approach, which sees costs and benefits shared between all market participants, especially households .
Trends and Indicators in Germany
Currently, renewable energy in Germany accounts for around 20% of the electricity generation, with solar PV contributing around 5% of Germany’s electricity demand (based on 2011 figures), however figures show that this is increasing as wind production decreases .
In Germany, installation of solar PV systems are growing rapidly with the support and subsidy schemes in place such as feed-in tariffs in order to provide households and industries with efficient wholesale prices, and fair, secure, and environmentally friendly energy sources. As a result, PV prices have dropped from around 14,000 €/kWp in 1990 to 1,600 €/kWp by end of 2012 . This shows a net-price regression of 89% over a period of 22 years, with a compound average price reduction rate of 9.4% . The use of subsidies is also used to cover supporting measures such as the costs of transmission and distribution grid expansion programmes, have had a significant affect on the viability of households being able to transition into using solar power . This has resulted in a decreased average price for PV Rooftop Systems in Germany (10kWp- 100kWp), from nearly 5000 euro in 2006 to just about 1500 euro in 2013 .
The capacity and performance of PV systems have improved significantly, allowing for the fast-growing trend of solar energy. According to the Fraunhofer Institute of Solar Energy in Germany, the performance ratio has increased from 70% to about 85% over the last 15 years. Cost reductions throughout the last 20 years have also become evident with prices decreasing by about 20% , with each doubling of the cumulated module production.
In 2011, PV plants produced 19.3 TWh, compared to 27.9 TWh in 2012, resulting in an increased production of 44% over a one year period . This demonstrates the rapidly growing market for renewable energy in Germany, including solar PV, and as a result, Germany achieved an export surplus of 22 TWh over 2011 .
In the case of Germany, solar PV has become favourable as a future energy supply, and is therefore highly supported by many policies known as Energiewende (Energy Concept). These legislation measures seek to achieve half of all electricity supply to come from renewable sources by 2030 .
The ‘sustainability’ mentality amoung politicians is an important driver for the success of solar PV growth, where the federal government has supported renewable energy for decades . By creating two key pieces of legislation including the Feed-in law (StrEG) of 1991 and subsequent policy (EEG) in 2000, federal, regional and local support systems were implemented in order to support investments of solar PV by subsides, tax incentives and soft loans. Programmes such as the 100,000 roof-programme, which provided debt finance for solar energy, also made PV economically viable for individuals . As a result, Germany is close to achieving the EU targets for clean energy, unlike its neighbouring counties . It also helps that the government has extensive public support in favour of renewable energy due to recent nuclear accidents such as Chernobyl and Fukushima, prompting a green-marketing system where almost 97% of Germans think that the support offered by the government in order to transition into solar energy is great .
The federal government has reportedly increased its research and development of solar energy, with budget funding increasing from EUR 1.9 billion over 2006-2009 to EUR 3.5 billion over 2011-2014 . This includes the creation of legislative measures to support renewables, as well as grid expansion, energy efficiency, and funding of reforms .
Regional Scale Trends - Middle EastAs of 2011 the Middle East is the world's largest source of Oil and Natural gas, they are not known for their renewable energy sources generating some hydro power and no solar power  (This has changed within the last year in some countries, for example Abu Dhabi).
Over 1000 CSP projects are planned is the MENA countries, most of them large in scale meant for major power supply, less than 100 of these are currently in construction and currently there are few finished projects. The potential for a large power industry is recognised and it will take time for this to be fully developed .
The Middle East is part of MENA (Middle East and Northern Africa), areas that have been identified due to their high solar irradiance as optimal sites for solar power infrastructure development .
The increasing cost of Oil power production has seen a huge increase in funding for solar power in the Middle East within the last year, Saudi Arabia plans to spend $109 billion on solar infrastructure through to 2032 , Abu Dhabi opened this year the world's largest CSP plant . What was once one of the biggest barriers to Solar Development in the Middle East is being lowered and the financial resources are available to create the infrastructure necessary. It is not only Middle Eastern governments that are interested in the Middle East. Through to 2050 Europe will not be likely to produce enough power for itself. Countries are looking to invest in solar infrastructure in the MENA countries so that power can be imported at reduced costs .
Regional Scale Trends - New Zealand
New Zealand currently is generating about 73% of its energy through renewable resources. However, Solar energy only accounts 0.1% of the total energy generated in New Zealand . Most of the applications of photovoltaic (PV) panels in New Zealand have been for residential and commercial hot water heating and stand alone (off grid) power systems. A 2007 report by Hydro Tasmania Consulting and the Energy Efficiency and Conservation Authority (EECA), found only 20 flat panel PV systems were feeding into New Zealand’s grid . The high principal cost of these systems leads to an increased price for the electricity which some people are willing to pay for. Despite common public perceptions, New Zealand has an excellent source of solar energy. The Solar irradiance table and NIWA's Mean Annual Sunshine Hours map demonstrate this. The EECA report found that price of PV systems is likely to reduce substantially by 2030, as indicated by the Projected PV cost table, but will still be around twice the price of grid-supplied electricity .
The New Zealand Government currently has a target of 90% renewable energy generation for the country by 2025 . However, the Ministry for the Environment states in their fifth national climate change publication that currently there are no government subsidies for new electricity generation in New Zealand .Most of the available government subsidies are targeted at energy efficiency, as renewable energy is already significant portion of New Zealand’s current electricity generation. The current government is also trying to reduce the regulatory barriers on the development of renewable energy resources .
Large Scale Generation
Currently the largest solar power plant in New Zealand was installed by South Auckland Forging Engineering in April 2012. The PV array can generate 68 kW and is expected to meet 70% of the companies’ electrical needs and is also setup to feed excess energy generated during summertime back into the national grid .
Stand Alone Power Systems - DOC Case Study
The Department of Conservation (DOC) recently installed stand alone power systems on five islands that they maintain. The power systems were not connected to an external electrical network and used a combination of photovoltaic panels, deep cycle batteries for electrical storage, a fossil fuel-based backup generator, and other electrical devices for managing the system . The new stand alone power systems were a replacement for the older systems which relied on diesel generators for the production of electricity on the islands.
The EECA along with DOC produced a study in 2010 to provide a comparative analysis of the power system upgrades for the five islands. The study found that while the initial cost of using solar energy technology was considerably higher, the life-cycle system cost is often cheaper than continual dependence on diesel generation . This is mainly due to the high cost of diesel fuel delivery to remote locations, as well as the maintenance cost of diesel generators. Photovoltaic panels have no moving parts and therefore the lowest maintenance overhead. They have a life expectancy of over 20 years and are considered to be one of the most reliable renewable generation technologies.
The new solar energy power systems saved DOC on annual operational costs from $41,221 on Tiritiri Matangi island to $1,999 on Motuihe Island as indicated in the table below . The annually operational cost savings for the five islands is $90,000 as well as a savings of 22,000 litres of diesel from use, and saving 60 tonnes of CO₂ from being emitted. Some of the non-financial benefits of the system that was found during the study were environmental impact, visitor’s perception, and opportunity cost. The islands are considered fragile environments the risk of contamination by diesel fuels was a significant threat. Installing the new solar power systems reduced this threat and also improved the air quality on the islands. Some of the islands have many tourists that visit each year, and one of DOC’s goals is to present these environments in a natural way. Using renewable energy sources will help to promote DOC’s conservation advocacy to the islands visitors. A result of continually maintaining diesel generators meant that DOC staff had a lost opportunity to work on other conservation tasks. Upgrading to a solar powered system resulted in an increase of staff time for other more meaningful tasks.
Environmental Impacts of Solar Energy
Although solar PV is seen as a “clean” and renewable energy source, utility-scale solar plants can be associated to a number of environmental impacts . Solar plants require vast quantities of land, and often along with construction of a plant, land disturbance and environmental degradation occurs within the designated area . Impacts on soil, air and water resources within area are often problematic, as well as loss of vegetation and wildlife habitats .
Production of solar panels is not an entirely “clean” process, as pollution occurs in many stages of construction such as whilst manufacturing, transporting and maintaining PV panels . However once in operation, there are no global warming emissions generated from solar electricity, where currently estimates of total life-cycle emissions for PV systems range from 0.07 to 0.18 pounds of CO2 per kilowatt-hour .
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