This paper presents a potable renewable energy system. The portable renewable energy power unit is designed from a need. The need is for first response teams in remote natural disaster situations to have a reliable source of energy to power a small vaccine refrigerator or water purification system and a basic satellite communication system. It is important that such a need is explored as a practical solution has the potential to save the lives of people in remote areas, who would otherwise suffer from a lack of humanitarian aid. Currently diesel generators are the primary source of electricity generation for disaster responders and in most situations work very well and provide a sufficient amount of electricity to meet the power needs. However, in remote areas road infrastructure is often damaged. In this type of situation getting a constant supply of diesel to the area is an expensive or impractical operation. This is where the portable renewable energy power unit bridges the gap and allows a more practical solution to be implemented. The specific aim of the work is to design a compact, stand-alone, product that can be easily transported by people across uneven terrain. It can generate power from wind, solar and hydro energy sources. In this work a new non-isolated multiport DC-DC converter topology for a hybrid energy system in low power applications is proposed. The new topology assimilates multiple renewable energy sources and power up multiple loads with different output levels. A complete Solid works model and FEA analysis, on required components, is completed. The scope of the work encompasses both the electrical and mechanical design of the system.
Currently diesel generators are the primary source of electricity generation for disaster responders and in most situations work very well and provide a sufficient amount of electricity to meet the power needs. However, in remote areas road infrastructure is often damaged. In this type of situation getting a constant supply of diesel to the area is an expensive or impractical operation. This is where the portable renewable energy power unit bridges the gap and allows a more practical solution to be implemented. This introduction section provides a background overview of the problems and ideas surrounding the research work.
Energy storage and power generation are some of the largest influences that have driven both the industrial and agricultural sectors in the developed world to what it is today [
There are few mobile, hybrid renewable energy systems for disaster relief on the market. Most of the systems currently on the market are singular systems usually consisting of solar generation and the hybrid systems that do exist have very inefficient methods of optimizing wind power capture. Adding energy generation sources has the potential to improve reliability of producing power in any environment. Furthermore, current systems usually need to be towed on a trailer. This makes it difficult to access areas where road infrastructure is damaged and makes it difficult for such systems because of size and weight to be transported into remote areas by air.
From reviewing the literature, it was found that there are two different types of hybrid systems in terms of the choice of energy generation that is currently being developed. The first systems are wind, solar hybrid systems and the second is wind, solar and diesel hybrid systems. The wind, solar, diesel generation hybrids still have the issue of needing access to diesel supply and still emit greenhouse gasses, however, these issues are reduced due to the backup of the solar and wind resources. A third concept that arose within the literature was described as “an ad-hoc self-organized micro-grid based on moveable and renewable energy sources and fully distributed co-ordination between intelligent power routing nodes” [
One article was about a product designed by a group of university students called the Mobile Elemental Power Plant (MEPP). This product is a wind, solar hybrid trailer system designed for the use of disaster relief and remote areas [
The system consists of two 240 watt solar panels and a 600 watt wind turbine that is fixed to a telescoping mast system that can raise the turbine 10 metres in the air to gain access of less turbulent, faster flowing air [
One issue related to renewable energy is its variability in its supply of electricity generation. Batteries can be integrated into a system to generate a more constant supply of power to users [
- Batteries,
- Flow batteries,
- Fuel cells,
- Fly wheels,
- Superconducting magnetic energy storage (SMES),
- Super capacitors,
- Compressed air energy storage,
- Pumped hydro.
Compressed air energy storage and pumped hydro are not sufficient for a movable micro-generation due to their size and weight. They are also very costly, therefore more appropriate for large scale energy systems. Super capacitors and SMES have high-power characteristics and their efficiencies are very good compared to other energy storage systems. They can also be drained and recharge numerous times without the capacity of energy storage being lost [
DC-DC converters are most common and are widely used in renewable energy systems to provide a controlled and regulated supply from an uncontrolled and unregulated renewable energy source [
・ It can accommodate multiple sources at the input.
・ Input sources can be employed independently and concurrently.
・ It can power up multiple loads with different voltage levels.
・ In addition to provide regulated output to the load, this converter can harvest maximum power from the input sources.
・ Surplus energy can be stored in the battery and made available in the absence of renewable energy sources.
The final solution as shown in
• A modular setup provides maximum adaptability when packing the system into confined spaces, such as a helicopter or truck, as it can be configured in many different ways to fit in with other supplies and resources.
• The modular design makes human transportation of the system easier as the weight of carrying each wheeled unit can be split between each team member. If the system was integrated as one large unit, the logistics of carrying the unit becomes a lot more difficult as multiple people would have to handle the unit at one time.
• The product is also a lot more adaptable as a modular system in terms of the weather conditions for each circumstance. It is not always necessary that all modules are taken where aid is needed. For example if the weather forecast for an effected remote area predicts a lot of sunshine but little wind and the area is not near a stream or river then it is practical to take only the solar and power storage unit as a power generating resource. In contrast, if the weather predicts rain, with little wind, but the affected area is near a constant flowing stream or river then it may be practical to just take the hydro and power storage unit. As demonstrated this provides a large amount of system adaptability and ensures no unnecessary weight and space is added to the aid supplies.
The new power system is designed to supply electricity to first responders to power their vital equipment. Furthermore the unit provides power redundancy when electricity cannot be produced from the renewable power sources (such as at night). The power generation sources run 12 V DC into the power unit through sockets in the side of the unit. The inputs then run into an Ampair 300 W regulator which regulates the current into the battery. There are two regulators as each regulator can only handle a maximum of two inputs. The battery is a 13.2 V, 100 Ah Lithium Ion Phosphate deep cycle battery, to provide up to 3 hours of redundancy for the system each day. From the battery there are two outputs, one AC and one DC. The AC output runs through a 200 W pure sine wave inverter and the DC output runs directly to a DC socket. In addition a 6 W cooling fan can be turned on, to cool the battery when necessary and all of the external components have rubber caps to seal them off from water or dust.
The solar array module is designed to capture the suns energy using photovoltaics and convert that energy into electricity, to be sent to the power storage unit. Three 55 W solar panels are connected in parallel to create a 12 V, 165 W solar array. A retractable 12 gauge cable that extends up to 6 metres enables the connection between the solar array and the power storage unit. The unit also has the capability to connect with an additional module to increase the power output in an area that receives a small amount of day light hours. An added solar array connects in parallel with the existing array in order to keep the 12 V output to the power storage unit. The solar arrays angle can be adjusted in order to face perpendicular to the sun at all times of the day, ultimately increasing the arrays power output capacity. The panels fold away into a tough high density polyethylene case which protects the panels from damage when transporting and storing and also protects them from adverse weather when not in use. The soft rubber caster wheels and retractable handle allow ease of human transportation across
rough surfaces such as gravel, grass or dirt roads.
Monocrystalline, Polycrystalline and thin film solar panels were considered for the solar array module. The most important factor for choosing the type of solar panel to use was the energy efficiency, as this system requires a high power output from a small, lightweight unit. While slightly more expensive, monocrystalline solar panels have the highest efficiency rates and were therefore chosen to be used on this design [
The wind module is designed to convert wind energy into electrical energy using a 300 W horizontal axis Am pair wind turbine. The turbine is elevated into the air, to a maximum of 6 meters in order to get into faster, more laminar flowing air. The 12 m long 12 gauge power cord runs from the wind turbine, down the inside of the telescopic tube and out the bottom of the mast holder. The cord has an excess of 6 metres to run to the power storage unit. While the turbine system is a large structure when set up, it can be packed up into a compact casing for transportation and storage. The handle and soft rubber wheels allow the case to be transported easily by a person across semi-rough terrain.
is the wind turbine out of its case before elevation, and in the right is the wind turbine at its maximum 6 m elevation, without its guy wires. While
The wind turbine module went through a range of design changes before arriving at the final design. Initially, like the other module designs, the stand for the turbine mast was integrated into the case. In this instance it was more practical to have the mast and stand separate from the case, due to the cases shape and size. A range of stand variations were investigated in the concept development stage, the final design was chosen due to its simplicity in the number of parts it uses which helps with reducing the weight of the product.
In order to have the turbine reach a setup height of 6 meters the mast material needs to be stiff, strong and lightweight. The two options that were considered for the mast material were aluminum and carbon fiber. As the wind turbine is supported near the top of the mast by guy wires the mast only needs to support a downward force of 1000 N (wind turbine), therefore, it can be assumed the strength of both the aluminum and carbon fiber (using 2 mm wall thickness) tube is of sufficient strength to support the wind turbine. Although slightly more expensive the carbon fiber tubing is 25% lighter than the aluminum and also has a greater stiffness and strength. Therefore carbon fiber tubing was chosen for the product and the weight benefits outweigh the slight increase in price from extruded aluminum.
The hydro turbine is designed to be placed into a stream or river and convert the energy from the moving water into electricity from the use of a turbine. As seen in
undone and the base of the module is flipped 180 degrees. The hydro turbine is then on the outside of the module and the wheels are housed inside the watertight unit as shown in
The multiport DC-DC buck converter is shown in
responsible for the control of battery charging and discharging process respectively and the switch Q 5 regulates the output voltage to a reference value.
In order to analyse the proposed converter, certain assumptions are made, i.e.
・ All the switches are ideal forward conducting reverse blocking.
・ All the losses are neglected.
・ V 1 , V 2 & V b > V o .
・ Output capacitor “C”, is large enough to smooth the output voltage “ V o ”.
・ It is assumed that the all the connected renewable energy sources are providing DC voltage corresponding to their maximum power point.
The new converter used dual input-single output mode for this application.
This mode of operation is applicable when a single voltage source in not able to satisfy the load demand and needs to be complemented by the second source and if the second voltage source is also not available, the energy stored in the battery can be utilized. This mode is further divided into two sub-modes. Energy transfer action from source to load depends on the control strategy adopted to generate the gate drive signals (Gs) to turn ON the switches Q 1 , Q 2 and/or Q 4 . There are numerous different arrangements to turn ON/ OFF the control switches in different switching states ( t 1 , t 2 , t 3 , t 4 ), however, six main switching schemes are defined here and shown in
• The switches Q 1 & Q 2 turned ON and OFF at the same time (
• The switches Q 1 & Q 2 turned ON at the same time but turn OFF time is different Q 2 turns OFF first (
• The switches Q 1 & Q 2 turned ON at the same time but turn OFF time is different Q 1 turns OFF first (
• The switches Q 1 & Q 2 are turned ON at different time ( Q 1 first) and turned OFF at the same time (
• Switch Q 1 turns ON and after an interval of time switch Q 2 turns ON. Switch Q 1 turns OFF first and switch Q 2 turns OFF later (
• Switch Q 1 turned ON for a period and then it is turned OFF. Whereas switch Q 2 is turned on when Q 1 is turned OFF (
The financial information that was considered in this work was the total material/component cost of the final product concept. The cost analysis is a very conservative estimate of costs as a lot of the cost estimates could only be based off the retail value of the components. For example the costs estimated for the solar panels, hydro turbine, and wind turbine are all considered using their retail cost. If a relationship is built with the suppliers and units are purchased in larger quantities, the cost of the components could be reduced significantly. The following are the conservative product part costings, in New Zealand dollars, for the system.
・ Power Unit $2269.
・ Solar Unit $1587.
・ Wind Unit $3300.
・ Hydro Unit $2583.
・ Total System Cost $9739.
Each module of the system will be sold separately, allowing customers to adapt their own system to the conditions that most align with the common area that they work within.
The portable power generation system is a practical design that fulfils the need for first response teams in remote natural disaster areas, to have a reliable source of energy, to power a small vaccine refrigerator or water purification system and a basic satellite communication system. The system design uses innovative features and materials in order to achieve a product that meets the design specifications of the application.
In this work a new non-isolated multiport DC-DC converter topology for a hybrid energy system in low power applications was presented. The new topology assimilates multiple renewable energy sources and power up multiple loads with different output levels. This new topology has ability to cope with different voltage level requirements and can integrate several energy sources to satisfy the variable load demands. The sources can be utilized independently or simultaneously. Surplus energy can also be stored and made available in case of absence of renewable energy sources.
The system fills a niche in the market for a self-sustaining power unit that can be successfully transported by foot or by air into affected remote disaster locations. Because the system is the only product of its kind, there is a reasonable opportunity for the adoption, by non-profit aid organizations who are involved in disaster relief, as natural disasters are always going to exist and are increasing with global warming. With the increase in renewable energy technologies, the long term success of such a product is promising.
The author wishes to thank the students and the workshop-technical staff at Massey University-School of Engineering and Advanced Technology for their help and support in this work.
Al-Bahadly, I. (2018) Portable Multi-Inputs Renewable Energy System for Small Scale Remote Application. Journal of Power and Energy Engineering, 6, 59-73. https://doi.org/10.4236/jpee.2018.62005