With photovoltaic cells to the sun

Photovoltaic cells are used to produce free energy not only in construction industry, but also as a support for energy supply of service facilities, road signs or electric vehicles. All over the world the scientists and designers are looking for solutions to the most efficient applications of photovoltaic cells. Many ideas have been already successfully implemented, but there are also extraordinary and costly ones that still have to wait to be brought to reality on a large scale.


Road signs and street lights

The active road signs are mainly installed in particularly dangerous places. They enable drivers to plan their manoeuvres earlier than in the case of usual, unlit signs, especially at night. The active road signs are visible from large distances and can warn about sharp bends or traffic islands and inform about pedestrian crossing etc. Implementation of energy saving LEDs allows to make use of solar energy in places where connection to standard power grid is not possible or is too expensive. In such cases, photovoltaic panels, wind turbines or their combinations, called hybrid systems, are used. Power supply parameters are set in such a way that the active road sign could work for 7-10 overcast days. The first solar powered active road sign in Poland was installed in 1999 by the pedestrian crossing at national road no. 2 in Halinów (about 10 km east of Warsaw). The project that has been conducted by Warsaw University of Technology and financed by the General Directorate of National Roads and Motorways, has proved that using solar powered road signs is profitable, even in our unfavourable climate. Thanks to monitoring systems of meteorological conditions and correct functioning of the road sign, the results of simulations are comparable to the reality. It helps to improve the project and construct more photovoltaic systems, to be used all around the country. The photovoltaic cells are also used on retroreflective road studs and elements mounted on crash barriers.


Glow on the dark roads

A special powder that glows up to 10 hours after dusk, working on the principle of solar lamps as well as a special paint for painting pedestrian crossings, which contains crystals that store solar energy and illuminate the crossings at nights, were developed in the Netherlands. Moreover, illuminated elements for so-called intelligent motorways, e.g. snowflakes warning about slippery road, are planned to be developed.



Hybrid lamps

Initially, solar powered lamps were being installed (so called Solar Street Lighting System) as universal illumination of e.g. pedestrian crossings or sharp bends. Nowadays, as in the case of active road signs, the system is often supported with wind energy. The hybrid devices are equipped in modern VRLA batteries which enable continuous functioning for several days (8–14 hours per day), regardless of weather conditions. Usually, the basic elements of the hybrid system are a LED road lantern, a photovoltaic panel, a wind turbine, a VRLA battery, a controller with a dusk sensor and finally, a lighting mast and lighting column. An autonomous Ledal lamp, developed and manufactured by Alumast, is one of the most interesting solutions of such type. It is distinguished by design of light fitting with LED-type source of light that is made of polymeric composites. Batteries, regulators as well as other system components can be placed inside the lamp. It is properly ventilated and at the same time, protected against leaking. A rotary dome, on the top of which a photovoltaic cell and a wind turbine were mounted, was installed on a column (with one or two jibs for lamps) made from polyester-glass composites. It enables choosing power supply sources and using them depending on needs and climate conditions. The lamp may be also equipped in an emergency supply system from power grid or a power generator. A universal structure of the lamp and jibs allows installing even up to 4 random light fittings with different angles of lighting and powered by renewable energy. The original idea of a self-sufficient lamp that does not require external sources of electricity, belongs to Kaal Masten. Its construction has 18 m in height, consists of LED lamps and a column, covered with photovoltaic cells, which collect the energy necessary to supply it. It is equipped with a system that that automatically turns the light on and off.


Solar motorways

Highway Solar Noise Wall in Netherlands or Solar Highway in Oregon are the examples in which the areas along the roads could be used for mounting photovoltaic cells on noise barriers or on special structures. The collected solar energy is used to supply electric vehicle charging stations and traffic lights on the road or in its vicinity. In Oregon, small solar farms have been installed by the roads, researched and improved since several years. However, it is still a quite expensive solution and the main problem is that the cells may get dirty and that lorries passing by the cells cast shadows at them. The Dutch innovative, transparent noise barriers (with min. 450 m in length and 6 m in height) have photovoltaic panels installed on both sides (at 2 m above ground) facing north-south. Covering the panels with self-cleaning glass, resistant to chemicals expected to become a solution to the problem of dirtiness. Completion of the prototype is scheduled for 2015, while the production is planned for the beginning of 2016.



Road surfaces to the sun

Solar roadways
Over the last few years, an innovative, almost bizarre Solar Roadway project has become more and more popular. According to its creators – an American couple Scott and Julia Brusaw from Idaho – the typical road surfaces would be replaced by photovoltaic cells. If they were implemented on majority of American roads, they would have produced three times more energy than is currently consumed in the United States. The basis of the invention are small (17 cm) hexagonal panels with special photovoltaic cells, covered with recycled toughened glass. The energy generated during the day would be stored and provided to local energy grids or used for inductive charging of electric vehicles, powering the lighting etc. All is to be connected to an intelligent system, aimed at automatic notification about damage of any panel or robbery attempt. Many LEDs may be placed into the panels and connected to form smart managed systems enabling display of e.g. horizontal signs, writings/communicates on the road, and also changes of traffic organisation or active marking of parking slots. The solar panels are to be equipped in heating elements that will melt the snow. The underground corridors with cable installation would also have space for rainwater drainage and storage systems. In 2010 the inventors created the first panels without solar cells in order to check if electronics worked properly. One year later, a heating system, LED lights and solar cells were installed. The ideas of solar roadways were awarded in GE Ecomagination Challenge contest (promoting technologies and solutions that help creating intelligent, green and efficient energy networks), and also EE Time ACE Awards in “The most promising renewable energy” category. This concept caught interest of the Federal Highway Administration, General Electric, and even Google. In order to gather more funds outside government grants, the project owners started a campaign on Indiegogo portal and managed to collect USD 2.2 million. After polishing the project and initial manufacturing, the inventors want to get to the 2nd phase of implementing the new technology, which is the covering of all American highways with the abovementioned panels.

Following the advantages of the characterised installation, its construction cost is also characterised by a quite acceptable price. As estimated in Scott Brusaw, each mile would cost around USD 4 million and will be especially effective in countries having high amount of sunshine. Durability of such roads is still questionable, even though the inventors assure that a single panel can withstand the weight of over 100 tones, which is more than the weight of the heaviest vehicles; however, it has not been completely proven yet. They also claim the tests conducted on wet glassy surface proved that a vehicle can get to a stop at about 129 km/h, while maintaining required distance. Also technological impediments may cause difficulties e.g. temperature fluctuations, precipitation, durability, wear and tear of panels’ surface at the point of contact with tyres, and also behaviour of such surface during a flood or an earthquake. The maintenance and repair costs are also significant, especially with difficult access to devices placed under the glass and in ducts. Despite the fact that the solar roadways have both supporters and opponents, the Brusaw couple are convinced in the relevance of their project and are confident in its prompt implementation. Similar solution – pavement made of photovoltaic panels – was developed by George Washington University (GWU) scientists in cooperation with the Spanish company Onyx. The prototype of the pavement surface was implemented on premises of the GWU campus – buildings of Exploration and Innovation Centre were connected with the pavement. The generated energy supplies as many as 450 LED lamps intended to illuminate the pavement.



The Dutch are quicker

The Dutch company SolaRoad is an originator, creator and general contractor of a project, being carried out in Krommenie (25 km north from Amsterdam). This year, a test section of a cycle route made of photovoltaic cells was officially opened. Currently it is a 70 m long path and ultimately it is supposed to reach 100 m in 2016 which should allow supplying of at least 3 households with electricity. The cycle route is made of prefabricated elements with a surface of 2.5 x 3.5 m, where under a 1 cm thick glass layer, silicone photovoltaic cells were installed. Dust and dirt, unfavourable gradient and the glass layer decrease the energy gains by about 30% in comparison to photovoltaic systems of similar power installed on roofs. The creators expect that the investment should capitalise after about 20 years, and in the case of massive production – in less than 15 years. That would probably be the first road in the world which construction costs capitalised in such a short time period. Construction of such kinds of routes could provide free electricity to power e.g. street lights, traffic lights, houses and even electric vehicles.


Solar paving blocks

Brick Lighting is a paving block with solar powered LEDs, equipped with a 1500–3000 mAh lithium battery and a dusk sensor which turns it on at sunset. A waterproof casing can withhold weight of several tones and that is why the bricks can be used both on pedestrian crossings, garden paths, parks, as well as driveways and public roads. The elements are resistant to ageing and UV radiation, they are also available in various sizes, shapes and colours (e.g. red, green, blue, yellow, white, pink and purple). The lighting can be controlled with a remote control with the functions such as 3 levels of colour brightness (brightening/dimming), increasing and decreasing the motion of displayed colours and turning the light on/off.



Electricity from the roof

Chargers of electric vehicles
Electric bikes and scooters charging stations constitute self-sufficient systems. It simply requires installing photovoltaic panels on their roofing. A station designed and produced by the Schrack Technik company may serve a good example of such technology. It has four panels that constitute the roof surface and protect against weather conditions. The station enables charging up to 6 vehicles at a time from power points placed on a column by each bicycle rack.Many open car parks with roofing are built, having photovoltaic cells installed on them. Some of them have a function of turning the panel’s direction, depending on weather conditions. In the autumn of 2014 one of the largest investments of this type was completed in Poland. There are almost 40 carports on the main car park of the University of Information Technology and Management in Rzeszow. Modern photovoltaic panels, having total surface area of about 840 sq. m. and generating about 170 kW of electricity, were installed on the carports. Each stand is equipped in Tesla and Melex power points that allow to charge 4 vehicles simultaneously.

Solar bridges

Covering about 3 km of roof over an Antwerp-Amsterdam high-speed rail tunnel is a very interesting solution. The mutual project of Infrabel (responsible for Belgian rail infrastructure) and Efinity (manufacturer of photovoltaic cells) companies is aimed at increasing the share of renewable energy sources in powering the rail. The photovoltaic cells, with total surface area of 50 000 sq. m. and installed on a special structure, generate 3.3 MWh annually. Thanks to that installation, completed in the middle of 2011, 4000 trains a year is powered by solar energy (normal and high-speed trains) which is a daily rail traffic as well as rail infrastructure and a train station in
Antwerp. It is the role model idea if one take into account the length of all railway tracks that could be roofed with solar collectors.

A similar solution was implemented on a rebuilt London’s railways bridge over Thames. The Solarcentury company mounted 4400 photovoltaic panels on a structure shielding the bridge. The panels will produce half of electric energy needed to power Blackfriars train station. It took almost 5 years to install the cells. Completing the investment was a great challenge. Free movement of structural elements and ensuring safety of the works was restricted by location of the bridge and continuous functioning of the train station while the bridge was being rebuilt. Such type of installation was also completed in Brisbane on a bridge for pedestrians and cyclists, where 84 photovoltaic panels were installed, thus, ensuring that total energy demand of the bridge is satisfied – 100 kW per day. Nowadays, more and more projects of solar powered bridges are created, e.g. in Seoul or Lisbon. Italian

design engineers created a project of a functional bridge that at the same time serves as a wind farm and solar power plant. It would generate as much as 40 million kWh of electricity that could power over 15 000 houses. Below, one can see the two other examples of innovative ideas for the use of roofing covered by photovoltaic cells that so far have not been implemented. One of the projects embraces the idea of 18 m long and 40 m high solar arcs on motorways – designed by TysonSteeleSolar Arch. The energy generated by them would supply lighting and prevent road icing. The second one is the project of a Swedish architect Hans Tham that lies in covering the Santa Monica Freeway highway in Los Angeles with solar panels.


Solar powered vehicles

Buses
The first solar powered bus Tindo was completed in 2007 in Adelaide in Australia. A Polish idea for using solar energy in transport resulted from cooperation of Lublin University of Technology and Municipal Transportation Office in Lublin during the conduction of the research project “Development of bus photovoltaic structures technology, limiting fuel consumption and emission of toxic components of exhaust fumes”. The outcomes of the cooperation may be seen in the form of the two 12-metre Mercedes Conecto buses with mounted photovoltaic panels which entered the streets of Lublin in autumn 2013. At the beginning of the previous year, the tests were conducted on another two 18-metre articulated buses. The installed panels are advanced, since thin-layer

photovoltaic cells, which are shock resistant and made of materials that make them flexible, ensure high absorption of solar spectrum.

City buses are being equipped in the increasing numbers of systems and devices e.g. lighting, ticket punches, ticket machines, bus stop displays, voice announcements and traffic management systems which significantly increase the demand for electric energy. According to professor Miroslaw Wendeker from the Department of Thermodynamics, Fluid Mechanics and Aviation Propulsion Systems in Lublin University of Technology, who is the project originator, the cells may supply 15–25% of energy used by the vehicle which should reduce fuel consumption by 4.5–5%. For comparison, identical panels were installed on the roof of 8-storey building of Lublin University of Technology. It was expected that the panel mounted on the roof of the bus should collect 63% less energy than the one that is completely exposed. However, as it turned out, that the loss amounts just to 25%. Research and development of the innovative technology from Lublin continued until 2015.


Rail

On the route of an inactive railway between Moerlenbach and Wald-Michelbach in Germany runs a solar powered electric rail. Thirty 8-person rail trolleys transport (at the speed of 30 km/h) , deliver tourists through railway bridges and two tunnels offering them amazing views. The passengers can also influence their physical condition by using pedals that work to additionally power the rail trolley. Other interesting projects of trains powered by solar energy are, for example, Hungarian touristic train called Vili Solar Train, Solar Bullet fast train in Arizona or single-track railway connecting Bologna and the main airport in Italy that in some places runs at the height of even 25 m. It is equipped with solar panels at every station and along the railway track, transferring gathered energy directly to the train. One of the many projects of the future is a track system of private transport, so-called JPods, capsules with own electric engines which draw energy from a special track by means of electric brushes similar to those which are used on the underground. The passengers call the capsule from a special station and after getting inside, they enter their destination by means of touch screens. Computer chooses an appropriate route and ensures that the two capsules do not crash with each other. A full-size capsule could run with a maximum speed of 48 km/h consuming approximately 150 Wh/km. Solar panels mounted on the tracks – with proper length – would be enough to provide energy for the entire system.

Cars

Cars powered by solar energy are usually treated as an attraction. Normally, they are designed for a single passenger and used for records beating. Creators of these bolides make their best to ensure that their model could travel the longest route on a single charge. World Solar Challenge can serve a good example. It is a race organised since 1987 in which vehicles powered by solar energy and recovered kinetic energy participate. Participants of the race, crossed the desert every day from 9 am to 5 pm covering the distance of 3000 km from Darwin to Adelaide. In 2013 the first in the world Stella family car, which was powered by solar energy, managed to successfully finish this race. It was created by students and doctoral students of Eindhoven University of Technology. It looks like a small, flat bus and it can accommodate 4 persons. On the car roof are located silicone solar collectors of high quality that cover half of the vehicle’s demand for energy. The car can cover 800 km using its battery only.The next World Solar Challenge race will take place in October 2017. Members of the Motorisation Enthusiasts Students’ Association of Lodz University of Technology (in cooperation with The Young Microelectronic Engineers’ Club of this University) were the first crew from Central and Eastern Europe that managed to create a vehicle, powered by solar energy for the Australian race.

 In 2015, the bolide took part in the race as a cruiser. It was designed for two passengers and complied with the parameters, required in normal road traffic. It was not an easy project since in time of panels’ installation on the surface of the vehicle, the creators had

to consider also the angle of light incidence (that is the latitude of the race route), driving direction (from north to south) as well as the season. Unfortunately, they did not manage to finish the race. Electric town cars presented by the Ford company during 2014 International CES are also interesting as they have photovoltaic panels on their roofs that allow easy charging without driver’s participation. Simply driving under a specially developed lens that focuses rays of light is enough.

Boats

Photovoltaic cells are also used to supply boats and yachts. In the last several years a few projects were created, e.g. Swiss Tûranor PlanetSolar – the world’s largest boat supplied only with solar power. A trimaran, launched a vessel in Germany in 2010, is 31 m long and it is covered with total photovoltaic cells surface area of 500 sq.m.. They generate approximately 93 kW for two electric engines and other on-board devices as well as for powerful lithium-ion batteries, thanks to which the boat can sail even for three stormy days without any problems. The structure of the trimaran ensures adequate stability, a shallow draught that saves energy used to power the unit, and a large deck area that can be covered with photovoltaic cells. The boat can reach a speed of about 15 sea

miles per hour. The first achievement of Tûranor was passing through the Atlantic Ocean within 26 days and 19 hours and in 2012 its crew sailed around the world within 584 days. Trimaran was adapted for cruise purposes for 12 passengers and a 4-person crew. In 2013 the previous record of passing through the Atlantic by this boat was beaten – it took only 22 days. Nowadays, it is used as a floating naval research laboratory by Geneva University.

Polish design engineers do not waste time as well. For example, Fiten Solar Team engineers from Gdynia in cooperation with Cree Yacht and Squall built a 6.2 m long and 2.45 m wide racing boat called Fiten Solar 2012 (improved model from 2011) which was one of the first boats in the world powered by solar power only. There is enough room for 6 people who could sail on inland waters, day and night without rest at an average speed of 8 km/h (max. up to 14).

 

Plane

Solar Impulse 2 is a plane that does not need any fuel. It is a result of 12-year cooperation of over seventy experts in calculations, simulations, designing and tests. The originators of it are Swiss pioneers Bertrand Piccard and André Borschberg. The first Solar Impulse 1 project gained 8 world records as a first solar plane able to fly during the night. It crossed two continents and flew over the United States. Version 2 is going to be the most revolutionary plane of all time created in order to fly all over the world, which means a continuous flight of five days and nights without fuel and with only one pilot inside. The weight of the plane is only 2300 kg and its huge wing is 72 m long (it is approximately equals the wingspan of Jumbo Jet) and it has 17 000 incorporated silicon cells, having total surface of 269.5 sq. m., supplying four electrical engines (each of 17.5 V). During the day the cells generate 340 kWh of electric power and charge lithium batteries weighing 633 kg that allow for flight at night. Currently, the Solar Impulse 2 project makes an attempt to fly around the globe. The aeroplane took off in Abu Dhabi and that also where it will finished its flight. As for now, the pilots managed to reach San Francisco on 24 April 2016. The originators of the project want to go around the globe by the end of 2016.

Analyzing the energy conditions of Poland, the scope of country’s resources and capabilities leads one to the conclusion that the country can be fully self-sufficient. Indeed, all the energy sources, so far known to humanity, are available here.