According to Socrates, the ideal home should be cool in summer and warm in winter. But Socrates' ideal was not easy to accomplish 2,500 years ago in ancient Greece. The Greeks had no artificial means of cooling their homes during the scorching summers; nor were their heating systems, mostly portable charcoal-burning braziers, adequate to keep them warm in winter.
Modern excavations of many Classical Greek cities show that solar architecture flourished throughout the area. Individual homes were oriented toward the southern horizon, and entire cities were planned to allow their citizens equal access to the winter sun. A solar-oriented home allowed its inhabitants to depend less on charcoal - conserving fuel and saving money.
Scottsdale requires a structural engineer report on the specific structure for residential PV and DHW. This costs a minimum of $500, usually higher. However, this has identified some potentially dangerous residences.
The Cities of Gilbert and Mesa do not require any permit for residential systems that do not involve changes to the main service electrical panel. The City of Mesa extends this to commercial systems. In Mesa the exemption includes the parking canopy construction as “just another mounting structure for the solar". A zoning review may be required in Mesa unless there are existing canopies and the solar canopy fits in with the others. However, if a building permit is needed in Mesa, it generally takes ‘only’ 20 working days, but Mesa is on a 4-day/week schedule so this means 5 weeks.
Plan review and permits generally add about 2% to the cost of a PV system.
The Cities of Gilbert and Mesa have generally accepted roof layout requirements intended to improve fire fighter safety in the event a house fire requires roof ventilation or other fire fighter roof access. Since building permits are not required, there is no formal check on this unless complaints are filed. There are many residential PV systems that do not conform to this requirement.
A recent project to install a covered parking canopy with a PV system on residential property in the City of Phoenix was a permit problem. In Phoenix simple PV systems can have a building permit issued ‘over the counter’ the same day with a set of properly designed plans. Not so simple with a large PV system on a separate parking canopy, located on a hillside lot. First of all, the Residential counter in the permit office takes a quick look at the plans and says “We are not staffed to review a parking structure, you need to go to the Commercial counter (another wait), then the Commercial counter looks up the property and states “This is residential, we cannot handle residential, go back to the Residential counter”. After insisting that the supervisors of these counters discuss this, they decide that two separate permits (structure and PV) are needed. The structure permit starts with a Site Plan that must include the square footages of the lot, hillside designated area, under roof area, disturbed areas, etc., all based on the original building permit for the lot many years ago. If the present owner of the lot does not have this information, one must wait for the City of Phoenix to search the archives. This took weeks and several meetings with zoning. Only after a building permit for the parking structure has been issued can a separate permit for the PV system be issued, and not over the counter. The whole procedure can take three months.
Concentrator photovoltaics (CPV) is a photovoltaic technology that generates electricity from sunlight. CPV photovoltaic systems use lenses and curved mirrors to focus sunlight onto small, but highly efficient, multi-junction (MJ) solar cells. To keep the sun focused on the relatively small solar cells, CPV systems use solar trackers to keep the focus on the solar cells and sometimes use a cooling system to further increase efficiency.
Some good general references are:
Green Rhino Energy- Concentrating Photovoltaics (CPV)
An Arizona example: Agua Caliente PV Power Plant Among World’s Largest
There are many barriers to wide scale adoption of photovoltaic systems in Arizona. Some of these are:
- Suitable installation area
- Electrical Code limits
- Building Code requirements
- Fire Code requirements
- Homeowner Association rules
- Electric Utility:
- Technical Limits
The cost of photovoltaic systems is continuing to decrease due to improvements in the technologies for photovoltaic modules and the inverters required to convert the dc electric power from the photovoltaic modules to regular ac electric power. Some items are increasing, such as wire, mounting structures, electrical apparatus (switches, meters, conduit). There are now many financing options to direct ownership that reduce or eliminate the upfront initial costs. The majority of residential photovoltaic systems being installed (2016) are now leased.
Many homes and commercial buildings simply do not have suitable areas for installing photovoltaic modules. Some residential developers actively design the roof orientations to make photovoltaic modules installation difficult or impossible, mostly because they find it easier to sell new homes in a development when they all look the same. This is not illegal, but is not in the spirit of an Arizona law (ARS: 33-439. Restrictions on installation or use of solar energy devices invalid; exception). There are utility restrictions on transporting electric power and water between properties, such as placing a photovoltaic on nearby property. More information on this is in <link to new article "Arizona Solar Laws">.
Safety is always a major concern. Except for some small low voltage photovoltaic systems (yard lights, etc.), many safety codes and standards apply in order to assure safe operation. The National Electrical Code, re-issued every three years, is the main electrical safety code, but there are requirements in Building and Fire codes that limit photovoltaic system installations. One relatively new requirement in the Building and Fire codes is to require clear access paths on roofs for first responders (firemen, etc.). Another relatively new requirement in the National Electrical Code (2017 version) requires that the roof mounted module area have an automatic shutdown such that when the ac power is disconnected all the voltages are reduced to safe levels (the dc voltages would otherwise increase when not connected). These requirements are generally reinforced in the building permit process.
In Arizona the electric utilities are essentially building barriers to photovoltaic systems by reducing direct and indirect incentives for photovoltaic systems. See the discussion in our Economics section Economics of Photovoltaics.
In some states, the electric utilities offer a billing option for Aggregated Net Billing wherein photovoltaic energy produced on one property or billing meter can be administratively applied to another account, perhaps with a small transaction fee.
Sometimes the existing utility electrical distribution system simply can not safely accept the proposed photovoltaic output. Those planning commercial size photovoltaic systems should check with the serving utility.
Recent (2015-2016) experience from an PV contractor: Some Barriers to Implementation of PV Systems