Photovoltaic system
A photovoltaic system, also called a PV system or solar power system, is an
PV systems convert light directly into electricity and are not to be confused with other solar technologies, such as
Operating silently and without any moving parts or environmental emissions, PV systems have evolved from niche market applications into a mature technology used for mainstream electricity generation. A rooftop system recoups the invested energy for its manufacturing and installation within 0.7 to 2 years and produces about 95 percent of net clean renewable energy over a 30-year service lifetime.[1]: 30 [2][3]
Due to the growth of photovoltaics, prices for PV systems have rapidly declined since their introduction; however, they vary by market and the size of the system. In 2014, prices for residential 5-kilowatt systems in the United States were around $3.29 per watt,[4] while in the highly penetrated German market, prices for rooftop systems of up to 100 kW declined to €1.24 per watt.[5] Nowadays, solar PV modules account for less than half of the system's overall cost,[6] leaving the rest to the remaining BOS components and to soft costs, which include customer acquisition, permitting, inspection and interconnection, installation labor, and financing costs.[7]: 14
Modern system
Overview
A
About 99 percent of all European and 90 percent of all U.S. solar power systems are connected to the
Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics is declining continuously.
As of 2015, the
Solar grid-connection
A grid connected system is connected to a larger independent grid (typically the public electricity grid) and feeds energy directly into the grid. This energy may be shared by a residential or commercial building before or after the revenue measurement point, depending on whether the credited energy production is calculated independently of the customer's energy consumption (
Scale of system
Photovoltaic systems are generally categorized into three distinct market segments: residential rooftop, commercial rooftop, and ground-mount utility-scale systems. Their capacities range from a few kilowatts to hundreds of megawatts. A typical residential system is around 10 kilowatts and mounted on a sloped roof, while commercial systems may reach a megawatt-scale and are generally installed on low-slope or even flat roofs. Although rooftop mounted systems are small and have a higher
Utility-scale
Large utility-scale
Rooftop, mobile, and portable
A small PV system is capable of providing enough AC electricity to power a single home, or an isolated device in the form of AC or DC electric. Military and civilian Earth observation
Building-integrated
In urban and suburban areas, photovoltaic arrays are often used on rooftops to supplement power use; often the building will have a connection to the
Performance
Uncertainties in revenue over time relate mostly to the evaluation of the solar resource and to the performance of the system itself. In the best of cases, uncertainties are typically 4% for year-to-year climate variability, 5% for solar resource estimation (in a horizontal plane), 3% for estimation of irradiation in the plane of the array, 3% for power rating of modules, 2% for losses due to dirt and
Components
A photovoltaic system for residential, commercial, or industrial energy supply consists of the solar array and a number of components often summarized as the balance of system (BOS). This term is synonymous with "Balance of plant" q.v. BOS-components include power-conditioning equipment and structures for mounting, typically one or more DC to AC power converters, also known as inverters, an energy storage device, a racking system that supports the solar array, electrical wiring and interconnections, and mounting for other components.
Optionally, a balance of system may include any or all of the following:
The terms "solar array" and "PV system" are often incorrectly used interchangeably, despite the fact that the solar array does not encompass the entire system. Moreover, "solar panel" is often used as a synonym for "solar module", although a panel consists of a string of several modules. The term "solar system" is also an often used misnomer for a PV system.
Solar array
The building blocks of a photovoltaic system are solar cells. A solar cell is the electrical device that can directly convert photons energy into electricity. There are three technological generations of solar cells: the first generation (1G) of
Conventional
Modules and efficiency
A typical 150 watt
The temperature effect on photovoltaic modules is usually quantified by means of some coefficients relating the variations of the open‐circuit voltage, of the short‐circuit current, and of the maximum power to temperature changes. In this paper, comprehensive experimental guidelines to estimate the temperature coefficients.[39]
Due to the low voltage of an individual solar cell (typically ca. 0.5V), several cells are wired (see Copper in renewable energy#Solar photovoltaic power generation) in series in the manufacture of a "laminate". The laminate is assembled into a protective weatherproof enclosure, thus making a photovoltaic module or solar panel. Modules may then be strung together into a photovoltaic array. In 2012, solar panels available for consumers had an efficiency of up to about 17%,[40] while commercially available panels can go as far as 27%. By concentrating the sunlight it is possible to achieve higher efficiencies. A group from The Fraunhofer Institute for Solar Energy Systems has created a cell that can reach 44.7% efficiency using the equivalent of "297 suns".[41][42][43][44]
Shading and dirt
Photovoltaic cell electrical output is extremely sensitive to shading (the so-called "Christmas light effect").[45][46][47] When even a small portion of a cell or of a module or array of cells in parallel is shaded, with the remainder in sunlight, the output falls dramatically due to internal 'short-circuiting' (the electrons reversing course through the shaded portion). When connected in series, the current drawn from a string of cells is no greater than the normally small current that can flow through the shaded cell, so the current (and therefore power) developed by the string is limited. If the external load is of low enough impedance, there may be enough voltage available from the other cells in a string to force more current through the shaded cell by breaking down the junction. This breakdown voltage in common cells is between 10 and 30 volts. Instead of adding to the power produced by the panel, the shaded cell absorbs power, turning it into heat. Since the reverse voltage of a shaded cell is much greater than the forward voltage of an illuminated cell, one shaded cell can absorb the power of many other cells in the string, disproportionately affecting panel output. For example, a shaded cell may drop 8 volts, instead of adding 0.5 volts, at a high current level, thereby absorbing the power produced by 16 other cells.[48] It is thus important that a PV installation not be shaded by trees or other obstructions. There are techniques to mitigate the losses with diodes, but these techniques also entail losses.
Several methods have been developed to determine shading losses from trees to PV systems over both large regions using
Most modules have bypass diodes between each cell or string of cells that minimize the effects of shading and only lose the power that the shaded portion of the array would have supplied, as well as the power dissipated in the diodes. The main job of the bypass diode is to eliminate hot spots that form on cells that can cause further damage to the array, and cause fires.Sunlight can be absorbed by dust, snow, or other impurities at the surface of the module (collectively referred to as soiling). Soiling reduces the light that strikes the cells, which in turn reduces the power output of the PV system. Soiling losses aggregate over time, and can become large without adequate cleaning. In 2018, the global annual energy loss due to soiling was estimated to at least 3–4%.[51] However, soiling losses vary significantly from region to region, and within regions.[52][53][54][55] Maintaining a clean module surface will increase output performance over the life of the PV system. In one study performed in a snow-rich area (Ontario), cleaning flat mounted solar panels after 15 months increased their output by almost 100%. However, 5° tilted arrays were adequately cleaned by rainwater.[28][56] In many cases, especially in
The long‐term reliability of photovoltaic modules is crucial to ensure the technical and economic viability of PV as a successful energy source. The analysis of degradation mechanisms of PV modules is key to ensure current lifetimes exceeding 25 years.[57]
Insolation and energy
Mounting
Modules are assembled into arrays on some kind of mounting system, which may be classified as ground mount, roof mount or pole mount. For
Cabling
Due to their outdoor usage, solar cables are designed to be resistant against
A solar cable is the interconnection
Specific performance requirements for material used for wiring a solar panel installation are given in national and local electrical codes which regulate electrical installations in an area. General features required for solar cables are resistance to ultraviolet light, weather, temperature extremes of the area and insulation suitable for the voltage class of the equipment. Different jurisdictions will have specific rules regarding grounding (earthing) of solar power installations for electric shock protection and lightning protection.
Tracker
A solar tracking system tilts a solar panel throughout the day. Depending on the type of tracking system, the panel is either aimed directly at the Sun or the brightest area of a partly clouded sky. Trackers greatly enhance early morning and late afternoon performance, increasing the total amount of power produced by a system by about 20–25% for a single axis tracker and about 30% or more for a dual axis tracker, depending on latitude.[65][66] Trackers are effective in regions that receive a large portion of sunlight directly. In diffuse light (i.e. under cloud or fog), tracking has little or no value. Because most
Trackers and sensors to optimise the performance are often seen as optional, but they can increase viable output by up to 45%.
For large systems, the energy gained by using tracking systems can outweigh the added complexity. For
As pricing, reliability and performance of single-axis trackers have improved, the systems have been installed in an increasing percentage of utility-scale projects. According to data from WoodMackenzie/GTM Research, global solar tracker shipments hit a record 14.5 gigawatts in 2017. This represents growth of 32 percent year-over-year, with similar or greater growth projected as large-scale solar deployment accelerates.[75]
Inverter
Systems designed to deliver alternating current (AC), such as grid-connected applications need an inverter to convert the direct current (DC) from the solar modules to AC. Grid connected inverters must supply AC electricity in sinusoidal form, synchronized to the grid frequency, limit feed in voltage to no higher than the grid voltage and disconnect from the grid if the grid voltage is turned off.[76] Islanding inverters need only produce regulated voltages and frequencies in a sinusoidal waveshape as no synchronisation or co-ordination with grid supplies is required.
A
Maximum power point tracking (MPPT) is a technique that grid connected inverters use to get the maximum possible power from the photovoltaic array. In order to do so, the inverter's MPPT system digitally samples the solar array's ever changing power output and applies the proper impedance to find the optimal maximum power point.[80]
Type | Power | Efficiency(a) | Market Share(b) |
Remarks |
---|---|---|---|---|
String inverter | up to 150 kWp(c) | 98% | 61.6% | Cost(b) €0.05-0.17 per watt-peak. Easy to replace. |
Central inverter | above 80 kWp | 98.5% | 36.7% | €0.04 per watt-peak. High reliability. Often sold along with a service contract. |
Micro-inverter
|
module power range | 90%–97% | 1.7% | €0.29 per watt-peak. Ease-of-replacement concerns. |
DC/DC converter (Power optimizer) |
module power range | 99.5% | 5.1% | €0.08 per watt-peak. Ease-of-replacement concerns. Inverter is still needed. |
Source: data by IHS Markit 2020, remarks by Fraunhofer ISE 2020, from: Photovoltaics Report 2020, p. 39, PDF watt-peak , (d) Total Market Share is greater than 100% because DC/DC converters are required to be paired with string inverters
|
Battery
Although still expensive, PV systems increasingly use rechargeable batteries to store a surplus to be later used at night. Batteries used for grid-storage also stabilize the electrical grid by leveling out peak loads, and play an important role in a smart grid, as they can charge during periods of low demand and feed their stored energy into the grid when demand is high.
Common battery technologies used in today's PV systems include the
PV systems with an integrated battery solution also need a charge controller, as the varying voltage and current from the solar array requires constant adjustment to prevent damage from overcharging.[83] Basic charge controllers may simply turn the PV panels on and off, or may meter out pulses of energy as needed, a strategy called PWM or pulse-width modulation. More advanced charge controllers will incorporate MPPT logic into their battery charging algorithms. Charge controllers may also divert energy to some purpose other than battery charging. Rather than simply shut off the free PV energy when not needed, a user may choose to heat air or water once the battery is full.
Monitoring and metering
The metering must be able to accumulate energy units in both directions, or two meters must be used. Many meters accumulate bidirectionally, some systems use two meters, but a unidirectional meter (with detent) will not accumulate energy from any resultant feed into the grid.[84] In some countries, for installations over 30 kWp a frequency and a voltage monitor with disconnection of all phases is required. This is done where more solar power is being generated than can be accommodated by the utility, and the excess can not either be exported or stored. Grid operators historically have needed to provide transmission lines and generation capacity. Now they need to also provide storage. This is normally hydro-storage, but other means of storage are used. Initially storage was used so that baseload generators could operate at full output. With variable renewable energy, storage is needed to allow power generation whenever it is available, and consumption whenever needed.
The two variables a grid operator has are storing electricity for when it is needed, or transmitting it to where it is needed. If both of those fail, installations over 30kWp can automatically shut down, although in practice all inverters maintain voltage regulation and stop supplying power if the load is inadequate. Grid operators have the option of curtailing excess generation from large systems, although this is more commonly done with wind power than solar power, and results in a substantial loss of revenue.[85] Three-phase inverters have the unique option of supplying reactive power which can be advantageous in matching load requirements.[86]
Photovoltaic systems need to be monitored to detect breakdown and optimize operation. There are several photovoltaic monitoring strategies depending on the output of the installation and its nature. Monitoring can be performed on site or remotely. It can measure production only, retrieve all the data from the inverter or retrieve all of the data from the communicating equipment (probes, meters, etc.). Monitoring tools can be dedicated to supervision only or offer additional functions. Individual inverters and battery charge controllers may include monitoring using manufacturer specific protocols and software.[87] Energy metering of an inverter may be of limited accuracy and not suitable for revenue metering purposes. A third-party data acquisition system can monitor multiple inverters, using the inverter manufacturer's protocols, and also acquire weather-related information. Independent smart meters may measure the total energy production of a PV array system. Separate measures such as satellite image analysis or a solar radiation meter (a pyranometer) can be used to estimate total insolation for comparison.[88] Data collected from a monitoring system can be displayed remotely over the World Wide Web, such as
Sizing of the photovoltaic system
Knowing the annual energy consumption in Kwh of an institution or a family, for example of 2300Kwh, legible in its electricity bill, it is possible to calculate the number of photovoltaic panels necessary to satisfy its energy needs. By connecting to the site https://re.jrc.ec.europa.eu/pvg_tools/en/ , after selecting the location in which to install the panels or clicking on the map or typing the name of the location, you must select "Grid connected" and "Visualize results" obtaining the following table for example relating to the city of Palermo:
Provided inputs:; Location [Lat/Lon]:;38.111,13.352 Horizon:;Calculated Database used:;PVGIS-SARAH2 PV technology:;Crystalline silicon PV installed [kWp]:;1 System loss [%]:;14 Simulation outputs:; Slope angle [°]:;35 Azimuth angle [°]:;0 Yearly PV energy production [kWh]:;1519.1 Yearly in-plane irradiation [kWh/m2]:;1944.62 Year-to-year variability [kWh]:;47.61 Changes in output due to:; Angle of incidence [%]:;-2.68 Spectral effects [%]:;0.88 Temperature and low irradiance [%]:;-7.48 Total loss [%]:;-21.88 PV electricity cost [per kWh]:;
Using the wxMaxima program, the number of panels required for an annual consumption of 2300 kWh and for a crystalline silicon technology with a slope angle of 35°, an azimut angle of 0° and total losses equal to 21.88% is 6 rounded up:
E_d : 2300 ;
E_s : 1519.1 ;
P : 300 ;
Number_panels : 1000 * E_d / ( P * E_s ) ;
5.046847914335243
On average, each family manages to consume 30% of energy directly from the photovoltaic. The storage system can bring its self-consumption to a maximum of 70%, therefore the battery storage capacity that should be in the specific case is: 4.41 Kwh which rounded up is 4.8 Kwh
Battery_capacity : 0.70 * E_d/365 ;
4.410958904109589
If the price of energy is 0.5 €/Kwh then the cost of energy excluding taxes will be 1150€ per year:
Energy_cost : E_d * 0.5;
1150.0
So if a 300W panel costs €200, the 4.8Kwh battery costs €3000, the inverter to convert the direct current into alternating current €1000, the charge regulator €100, the installation costs €1000 the total cost will be €6,300 :
Total_cost : 200*6 + 3000 + 1000 + 100 + 1000 ;
3150
which are amortized over 5.46 years:
Years : Total_cost / Energy_cost ;
5.46...
having the battery a life of 10 years and the panels 25–30 years
Other systems
This section includes systems that are either highly specialized and uncommon or still an emerging new technology with limited significance. However, standalone or off-grid systems take a special place. They were the most common type of systems during the 1980s and 1990s, when PV technology was still very expensive and a pure niche market of small scale applications. Only in places where no electrical grid was available, they were economically viable. Although new stand-alone systems are still being deployed all around the world, their contribution to the overall installed photovoltaic capacity is decreasing. In Europe, off-grid systems account for 1 percent of installed capacity. In the United States, they account for about 10 percent. Off-grid systems are still common in Australia and South Korea, and in many developing countries.[8]: 14
CPV
Concentrator photovoltaics (CPV) and high concentrator photovoltaic (HCPV) systems use
Especially HCPV systems are best suited in location with high solar irradiance, concentrating sunlight up to 400 times or more, with efficiencies of 24–28 percent, exceeding those of regular systems. Various designs of systems are commercially available but not very common. However, ongoing research and development is taking place.[1]: 26
CPV is often confused with CSP (concentrated solar power) that does not use photovoltaics. Both technologies favor locations that receive much sunlight and directly compete with each other.
Hybrid
A hybrid system combines PV with other forms of generation, usually a diesel generator. Biogas is also used. The other form of generation may be a type able to modulate power output as a function of demand. However more than one renewable form of energy may be used e.g. wind. The photovoltaic power generation serves to reduce the consumption of non renewable fuel. Hybrid systems are most often found on islands. Pellworm island in Germany and Kythnos island in Greece are notable examples (both are combined with wind).[93][94] The Kythnos plant has reduced diesel consumption by 11.2%.[95]
In 2015, a case-study conducted in seven countries concluded that in all cases generating costs can be reduced by hybridising mini-grids and isolated grids. However, financing costs for such hybrids are crucial and largely depend on the ownership structure of the power plant. While cost reductions for state-owned utilities can be significant, the study also identified economic benefits to be insignificant or even negative for non-public utilities, such as independent power producers.[96][97]
There has also been work showing that the PV penetration limit can be increased by deploying a distributed network of PV+CHP hybrid systems in the U.S.[98] The temporal distribution of solar flux, electrical and heating requirements for representative U.S. single family residences were analyzed and the results clearly show that hybridizing CHP with PV can enable additional PV deployment above what is possible with a conventional centralized electric generation system. This theory was reconfirmed with numerical simulations using per second solar flux data to determine that the necessary battery backup to provide for such a hybrid system is possible with relatively small and inexpensive battery systems.[99] In addition, large PV+CHP systems are possible for institutional buildings, which again provide back up for intermittent PV and reduce CHP runtime.[100]
- PVT system (hybrid PV/T), also known as photovoltaic thermal hybrid solar collectors, convert solar radiation into thermal and electrical energy. Such a system combines a solar (PV) module with a solar thermal collector in a complementary way.
- concentrated photovoltaics(CPV) instead of conventional PV technology, and combines it with a solar thermal collector.
- CPV/CSP system is a proposed novel solar hybrid system, combining concentrator photovoltaics with the non-PV technology of concentrated solar power (CSP), or also known as concentrated solar thermal.[101]
- other renewables are possible and include wind turbines.[103]
Floating solar arrays
The systems can have advantages over photovoltaics (PV) on land. Water surfaces may be less expensive than the cost of land, and there are fewer rules and regulations for structures built on bodies of water not used for recreation. Life cycle analysis indicates that foam-based FPV[109] have some of the lowest energy payback times (1.3 years) and the lowest greenhouse gas emissions to energy ratio (11 kg CO2 eq/MWh) in crystalline silicon solar photovoltaic technologies reported.[110]
Floating arrays can achieve higher efficiencies than PV panels on land because water cools the panels. The panels can have a special coating to prevent rust or corrosion.[111]
The market for this renewable energy technology has grown rapidly since 2016. The first 20 plants with capacities of a few dozen kWp were built between 2007 and 2013.[112] Installed power grew from 3 GW in 2020, to 13 GW in 2022,[113] surpassing a prediction of 10 GW by 2025.[114] The World Bank estimated there are 6,600 large bodies of water suitable for floating solar, with a technical capacity of over 4,000 GW if 10% of their surfaces were covered with solar panels.[113]
The costs for a floating system are about 10-20% higher than for ground-mounted systems.[115][116]Direct current grid
DC grids are found in electric powered transport: railways trams and trolleybuses. A few pilot plants for such applications have been built, such as the tram depots in Hannover Leinhausen, using photovoltaic contributors[117] and Geneva (Bachet de Pesay).[118] The 150 kWp Geneva site feeds 600 V DC directly into the tram/trolleybus electricity network whereas before it provided about 15% of the electricity at its opening in 1999.
Standalone
A
A charge controller may be incorporated in the system to avoid battery damage by excessive charging or discharging. It may also help to optimize production from the solar array using a maximum power point tracking technique (MPPT). However, in simple PV systems where the PV module voltage is matched to the battery voltage, the use of MPPT electronics is generally considered unnecessary, since the battery voltage is stable enough to provide near-maximum power collection from the PV module. In small devices (e.g. calculators, parking meters) only
In
Costs and economy
in Japan, Germany and the United States ($/W)
Graphs are unavailable due to technical issues. There is more info on Phabricator and on MediaWiki.org. |
The cost of producing photovoltaic cells has dropped because of economies of scale in production and technological advances in manufacturing. For large-scale installations, prices below $1.00 per watt were common by 2012.[122] A price decrease of 50% had been achieved in Europe from 2006 to 2011, and there was a potential to lower the generation cost by 50% by 2020.[123] Crystal silicon solar cells have largely been replaced by less expensive multicrystalline silicon solar cells, and thin film silicon solar cells have also been developed at lower costs of production. Although they are reduced in energy conversion efficiency from single crystalline "siwafers", they are also much easier to produce at comparably lower costs.[124]
The table below shows the total (average) cost in US cents per kWh of electricity generated by a photovoltaic system.
The calculated values in the table reflect the total (average) cost in cents per kWh produced. They assume a 10% total capital cost (for instance 4%
Cost of generated kilowatt-hour by a PV system (US¢/kWh) depending on solar radiation and installation cost during 20 years of operation | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Installation cost in $ per watt |
Insolation annually generated kilowatt-hours per installed kW-capacity (kWh/(kWp•y))
| ||||||||||||
2,400 | 2,200 | 2,000 | 1,800 | 1,600 | 1,400 | 1,200 | 1,000 | 800 | |||||
$0.20 | 0.8 | 0.9 | 1.0 | 1.1 | 1.3 | 1.4 | 1.7 | 2.0 | 2.5 | ||||
$0.60 | 2.5 | 2.7 | 3.0 | 3.3 | 3.8 | 4.3 | 5.0 | 6.0 | 7.5 | ||||
$1.00 | 4.2 | 4.5 | 5.0 | 5.6 | 6.3 | 7.1 | 8.3 | 10.0 | 12.5 | ||||
$1.40 | 5.8 | 6.4 | 7.0 | 7.8 | 8.8 | 10.0 | 11.7 | 14.0 | 17.5 | ||||
$1.80 | 7.5 | 8.2 | 9.0 | 10.0 | 11.3 | 12.9 | 15.0 | 18.0 | 22.5 | ||||
$2.20 | 9.2 | 10.0 | 11.0 | 12.2 | 13.8 | 15.7 | 18.3 | 22.0 | 27.5 | ||||
$2.60 | 10.8 | 11.8 | 13.0 | 14.4 | 16.3 | 18.6 | 21.7 | 26.0 | 32.5 | ||||
$3.00 | 12.5 | 13.6 | 15.0 | 16.7 | 18.8 | 21.4 | 25.0 | 30.0 | 37.5 | ||||
$3.40 | 14.2 | 15.5 | 17.0 | 18.9 | 21.3 | 24.3 | 28.3 | 34.0 | 42.5 | ||||
$3.80 | 15.8 | 17.3 | 19.0 | 21.1 | 23.8 | 27.1 | 31.7 | 38.0 | 47.5 | ||||
$4.20 | 17.5 | 19.1 | 21.0 | 23.3 | 26.3 | 30.0 | 35.0 | 42.0 | 52.5 | ||||
$4.60 | 19.2 | 20.9 | 23.0 | 25.6 | 28.8 | 32.9 | 38.3 | 46.0 | 57.5 | ||||
$5.00 | 20.8 | 22.7 | 25.0 | 27.8 | 31.3 | 35.7 | 41.7 | 50.0 | 62.5 | ||||
Notes:
|
Learning curve
Photovoltaic systems demonstrate a learning curve in terms of levelized cost of electricity (LCOE), reducing its cost per kWh by 32.6% for every doubling of capacity.[132][133][134] From the data of LCOE and cumulative installed capacity from International Renewable Energy Agency (IRENA) from 2010 to 2017,[133][134] the learning curve equation for photovoltaic systems is given as[132]
- LCOE : levelized cost of electricity (in USD/kWh)
- Capacity : cumulative installed capacity of photovoltaic systems (in MW)
Regulation
Standardization
Increasing use of photovoltaic systems and integration of photovoltaic power into existing structures and techniques of supply and distribution increases the need for general standards and definitions for photovoltaic components and systems.[citation needed] The standards are compiled at the International Electrotechnical Commission (IEC) and apply to efficiency, durability and safety of cells, modules, simulation programs, plug connectors and cables, mounting systems, overall efficiency of inverters etc.[135]
National regulations
United Kingdom
In the UK, PV installations are generally considered permitted development and do not require planning permission. If the property is listed or in a designated area (National Park, Area of Outstanding Natural Beauty, Site of Special Scientific Interest or Norfolk Broads) then planning permission is required.[136]
United States
In the United States, article 690 of the National Electric Code provides general guidelines for the installation of photovoltaic systems; these may be superseded by local laws and regulations. Often a permit is required necessitating plan submissions and structural calculations before work may begin. Additionally, many locales require the work to be performed under the guidance of a licensed electrician.
The
Spain
Although Spain generates around 40% of its electricity via photovoltaic and other renewable energy sources, and cities such as Huelva and Seville boast nearly 3,000 hours of sunshine per year, in 2013 Spain issued a solar tax to account for the debt created by the investment done by the Spanish government. Those who do not connect to the grid can face up to a fine of 30 million euros (US$40 million).[142] Such measures were finally withdrawn by 2018, when new legislation was introduced banning any taxes on renewable energy self-consumption.[143]
Limitations
Impact on electricity network
With the increasing levels of rooftop photovoltaic systems, the energy flow becomes two-way. When there is more local generation than consumption, electricity is exported to the grid. However, electricity network traditionally is not designed to deal with the two-way energy transfer. Therefore, some technical issues may occur. For example, in Queensland, Australia, there have been more than 30% of households with rooftop PV by the end of 2017. The famous Californian 2020 duck curve appears very often for a lot of communities from 2015 onwards. An over-voltage issue may come out as the electricity flows back to the network.[144] There are solutions to manage the over voltage issue, such as regulating PV inverter power factor, new voltage and energy control equipment at electricity distributor level, re-conductor the electricity wires, demand side management, etc. There are often limitations and costs related to these solutions. A way to calculate these costs and benefits is to use the concept of 'value of solar' (VOS),[145] which includes the avoided costs/losses including: plant operations ans maintenance (fixed and variable); fuel; generation capacity, reserve capacity, transmission capacity, distribution capacity, and environmental and health liability. Popular Mechanics reports that VOS results show that grid-tied utility customers are being grossly under-compensated in most of the U.S. as the value of solar eclipses the net metering rate as well as two-tiered rates, which means "your neighbor's solar panels are secretly saving you money".[146]
Implications for electricity bill management and energy investment
Customers have different specific situations, e.g. different comfort/convenience needs, different electricity tariffs, or different usage patterns. An electricity tariff may have a few elements, such as daily access and metering charge, energy charge (based on kWh, MWh) or peak demand charge (e.g. a price for the highest 30min energy consumption in a month). PV is a promising option for reducing energy charge when electricity price is reasonably high and continuously increasing, such as in Australia and Germany. However, for sites with peak demand charge in place, PV may be less attractive if peak demands mostly occur in the late afternoon to early evening, for example residential communities. Overall, energy investment is largely an economic decision and investment decisions are based on systematical evaluation of options in operational improvement, energy efficiency, onsite generation and energy storage.[147][148]
See also
- Copper conductor
- Polyolefin
- Low smoke zero halogen
- MC4 connector
- Solar micro-inverter
- Tinning
- Energy demand management
- List of photovoltaic power stations
- List of rooftop photovoltaic installations
- Panel generation factor
- Photovoltaic power station
- Renewable energy
- Rooftop photovoltaic power station
- Solar energy
- Solar vehicle
References
- ^ a b c d e f g "Photovoltaics Report" (PDF). Fraunhofer ISE. 28 July 2014. Archived (PDF) from the original on 9 August 2014. Retrieved 31 August 2014.
- ^ Service Lifetime Prediction for Encapsulated Photovoltaic Cells/Minimodules, A.W. Czanderna and G.J. Jorgensen, National Renewable Energy Laboratory, Golden, CO.
- ^ .
- ^ "Photovoltaic System Pricing Trends – Historical, Recent, and Near-Term Projections, 2014 Edition" (PDF). NREL. 22 September 2014. p. 4. Archived (PDF) from the original on 26 February 2015.
- ^ "Photovoltaik-Preisindex" [Solar PV price index]. PhotovoltaikGuide. Archived from the original on 10 July 2017. Retrieved 30 March 2015.
Turnkey net-prices for a solar PV system of up to 100 kilowatts amounted to Euro 1,240 per kWp.
- ^ Fraunhofer ISE Levelized Cost of Electricity Study, November 2013, p. 19
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Further reading
- Sonnenenergie, Deutsche Gesellschaft für (2008). Planning and installing photovoltaic systems: a guide for installers. Earthscan. ISBN 978-1-84407-442-6.
External links
- Summary of Photovoltaic Wire Requirements as Outlined in UL 4703
- Photovoltaic Energy Factsheet by the University of Michigan's Center for Sustainable Systems
- Home Power Magazine
- Solar project management
- Best Practices for Siting Solar Photovoltaics on Municipal Solid Waste Landfills: A Study Prepared in Partnership with the Environmental Protection Agency for the RE-Powering America's Land Initiative: Siting Renewable Energy on Potentially Contaminated Land and Mine Sites National Renewable Energy Laboratory