Photovoltaic solar energy applications

The energy obtained through photovoltaic generators and their applications is greatly diverse.

If a general classification is established, it can be said that it is divided into two large sections:

  • Isolated systems
  • Grid connection

Atersa has carried out projects in both applications, some examples are detailed below:


Isolated systems

  • Telecommunications
  • Rural electrification
  • Agricultural applications
  • Used with livestock/cattle
  • Street lighting
  • Signage
  • Control
  • Rural development

A short analysis of each of them has been made below, elaborating the previous sections:

Telecommunications:

  • Mobile phone
  • Radio and television repeaters
  • Roadside S.O.S. posts
  • Remote control
  • Remote control for irrigation systems
  • Telemetry
  • Radars
  • Radiotelephony in general and for militaries or forest surveillance posts
  • Rural telephones via satellite
  • Microwave
  • Public telephone booths
  • Communication stations
  • Radio links
  • TRUNKING systems
  • Radio and communication coverage in railway tunnels

There are two kinds of stations for mobile phones, BTS calls, made up of a photovoltaic-diesel hybrid system, with a photovoltaic peak power of 6 Kwp, in which the function of the generator is only for support.

The second kind of installations are called RF calls, which only function with rotating photovoltaic panels and an installed peak power between 0.6 Kwp and 1.8 Kwp.

The remote controls and telecommands with radio transmission are often used in applications related to water, tanks, risks, flowmetres and, in general, for collecting and controlling any kind of data.

Rural electrification:

  • Temporary housing
  • Permanent housing
  • Centralised electrification with individual consumption control per house, in rural areas
  • Refuge and mountain lodge electrification
  • Aid stations. (lighting, medication and vaccine preservation with refrigerators)
  • Schools and community centres
  • Police stations and borders
  • Religious facilities (chapels, missions, etc.)

Rural electrification currently has all of the commodities that a conventional electrification system can have since the incorporation of new sine wave inverters, allowing for the use of any appliance.

One of the most important applications is currently the electrification of small rural areas with centralised systems. The advantages with respect to one installation per house are the following:

  • Lower installation cost
  • Lower maintenance costs
  • Higher level of user friendliness
  • Higher security of the facility
  • Greater total return

To manage the energy, an energy limiting electronic device is installed in each of the houses that is programmed to be able to supply energy to the user every day. That being said, the device has to be intelligent enough to be able to increase the assigned energy, if the batter status is good or bad. To simplify and not perform complicated electrical wiring, the communication between the energy limiting device and the inverters is made along the same 220 Vac line, with small changes in frequency that do not affect the operation of the system in any way.

The second greatest inconvenience is the power of the inverter and its efficiency against small charges. This was resolved with the installation of several inverters in parallel, with one of them (the master) being that which acts on the control of the rest (the slaves), so that if the power consumed is less than the sum of the power of all the inverters, it orders some of them to stop until they adapt to the consumed power. Another great advantage is that all of the inverters have the capacity to act as masters and as slaves. With this, the electrical supply is secured against possible failures in some of them.

Agricultural applications

  • Water pumps both in DC and AC (with battery)
  • Direct drive water pumps (without battery)
  • Warehouse electrification
  • Risk controls
  • Greenhouses (automation of windows and lighting)

One of the most important applications in agriculture, for its simple installation and above all for its zero maintenance and complete automation, are the direct drive water pumps, made up of a field of photovoltaic panels, an electronic device and the entire system of controls and pump sensors.

The aforementioned electronic device has the capacity to obtain the maximum performance of the panel in low flow pumps. In high flow pumps, it has a second function, which is to convert the continuous current of the photovoltaic panel into alternating current.

The main advantage of the direct drive pumps is that they coincide with the radiation curve and the water demand curve. They allow for water extraction in rural environments, where the possibility to install a conventional line does not exist due to its high cost.

A second application in the agricultural sector has been the electrification of risk controls and solenoid valves, which has allowed for a better distribution and saving of water. They are mostly systems based on the risk of leaks or low pressure.

Used with livestock/cattle :

  • Water pumps to provide water to the livestock/cattle
  • Farm electrification. (lighting, motors, shearing machines, etc.)
  • Milking systems and milk refrigeration
  • Fence electrification

The direct drive pumps, detailed under farmland applications, are at the cattle farms, a highly important location.

The manufacture of high power inverters has made it possible to undertake works at the cattle farm, supply electrical energy to milking systems, preserve milk (cold tanks) and clean pumps, as well as to light up warehouses, power motors for the distribution of animal feed, fans, automation of shutters for cattle warehouses and greenhouses. The motors of the aforementioned equipment, originally and to achieve a higher performance at the facility, were installed in DC. Then, thanks to the new high performance inverters, the motors are now in AC, obtaining a greater operational safety in the event of failure since an alternating motor is easy to obtain, while a continuous one is specially produced.

The installed inverter, to provide more safety to the system, is modular with several power stages so that they can be repaired without the system running out of power.

Lighting:

  • Billboards
  • Public streetlights
  • Bus stops
  • Tunnel, cave, etc. lighting

Public lighting, through photovoltaic systems, is presented as one of the most economic solutions to light the entrances of the towns, road junctions, rest areas, etc.

A new type of street light is currently being installed, which does not require any maintenance, by integrating long life stationary batteries with gelled electrolytes (over 300 streetlights in the Canary Islands).

Signage:

  • Lighthouses and marine buoys
  • Air beacons and radio beacons
  • Road signs to indicate curves, obstacles, roundabouts, etc. in cities and on roadways using LEDs
  • Time and temperature indicators on public roads
  • Railway crossings
  • Oil rigs

The use of the ESF has allowed for the automation of lighthouses, as well as an increase in buoy safety, where acetylene gel was previously used, significantly reducing maintenance.

For aviation use, panels to supply the beacons and road signs on the runways are being used. The Madrid and Balearic airports stand out for their easy identification of facilities.

Another wide application, which has recently been added to road safety with a great importance, is the labelling of roundabouts, curves, traffic signs, obstacles, etc. through the use of high luminosity LEDs, which, because of their low consumption, makes it possible to make a small photovoltaic installation.

Control:

  • Flowmetres and anemometers
  • Activation of valves (solenoid valves)
  • Controls, weather stations and earthquakes
  • TV cameras to control and measure traffic
  • Monitoring and automation of gates
  • Fibre optic signal repeaters
  • Environment metering stations
  • Gas and oil pipeline control
  • Data collection
  • Control and remote operation of reservoirs
  • Cathodic protection

In this section, it is currently worth mentioning that works are being performed on the river basins to control the flow and quality of the water, where the photovoltaic systems are found, as well as those that are more economic and secure for these types of applications.

The photovoltaic installations have shown high reliability in greatly important applications and large projects, such as the gas and oil pipelines, where they are responsible for providing electrical energy to the control, communication, valve activation and cathodic protection systems. This previous application is also used on bridges.

Other applications:

  • Chlorination through dosing pumps
  • Purification through lagooning by supplying clean-grille motors and flowmetres
  • Oxygenators for the water through compressors
  • Salt water desalination (reverse osmosis)
  • Scales to weigh lorries. (landfills, industrial centres, etc.)
  • Systems to detect fires by means of infrared cameras
  • Infrared perimeter security systems
  • Surveillance and access control (video intercom, opening and closing of gates, remote control)
  • Ionisation for lightning rods
  • Power supply for didactical uses at universities, professional colleges, etc.
  • Sailing vessels and motor homes
  • Recreational area equipment

The second largest group of the photovoltaic systems are those connected to the electricity grid:

Systems connected to the electricity grid

It is one of the latest and most innovative applications of the photovoltaic systems, consisting of the installation of a photovoltaic field and inverter capable of transforming the energy supplied by the panels and pumping it into the electricity grid.

The inverter in this type of installation is the central nucleus inverter and must provide certain protections against situations that may occur in the electricity grid, such as:

  • Out-of-range voltage
  • Grid cut
  • Discrepancy in the grid

To obtain economic viability of these systems, the country must provide a legal standard and economic aid lines, which compensate the increased cost per Kwh generated.