It is now well known, as well as RIDS-Nepal’s practical experience, gained over the last 16 years, that access to improved energy services, such as stove (for cooking and room heating) which carries the smoke outside the kitchen or basic indoor lighting, is an important part of community development, aiming to improve impoverished communities’ living conditions.

In order to improve the access to energy services it is crucial to have suitable and sustainable resources of energy available. These are for most remote, high altitude Himalayan village communities in Nepal, with whom RIDS-Nepal is working, the local available renewable energy resources such as the energy contained in sunshine, the wind, local streams and river, biomass (if used sustainable), and in various areas available through geothermal energy resources.

RIDS-Nepal has since the late 90’s developed new concepts and technologies to tap into the various RE (Renewable Energy) resources, and to convert them into more useful energy services, such as electricity for basic indoor lighting (click here), heat (for cooking, room heating (click here) or hot water for improved hygiene (click here), improved agricultural production through greenhouses (click here) as well as other applications.

RIDS-Nepal has also learnt that contextualized (for a defined context developed technologies) and installed RETs (Renewable Energy Technologies) play a central role in a long-term holistic community development project in partnership with a local village community. This, as people’s needs to be addressed are most commonly not met through addressing just one individual problem, but the need for better living conditions is made up of many different needs, which all have to be identify and addressed alongside each other over the course of a project’s life cycle.

Thus any community development project approach has to consider a holistic, multi-faceted, long-term approach, rather than a mere single-oriented, short-term project approach. Thus, technical projects should never be considered in isolation of educational, health and social projects. Hence, neither should “just” health, or “just” educational or “just” social oriented projects be implemented in isolation of all other fields of expertise, as people’s needs and problems are always multi-faceted.

This learning has been the basis for the creation of RIDS-Nepal’s long-term holistic community development concepts the “Family of 4” and the “Family of 4 PLUS”, which include possible solutions to needs and problems the local village communities themselves have identified and RIDS-Nepal has worked over the years on contextualized solutions.

However, in the project we present here we focus on a Solar Photovoltaic (PV) – Wind Turbine (WT) RAPS (Remote Area Power Supply) Hybrid System, in order to utilize not just one local available RE resource but multiple renewable RE resources, so that remote located village communities, with no hope for any future grid connection, can consider to tap into their own local renewable energy resources and convert them through various contextualized renewable energy technologies into useful energy services such as e.g. electricity.

The following schemata shows the basic idea of a RAPS Hybrid system, utilizing the local available wind and solar energy to provide the daily energy demands for a household, a whole village, a school or even a hospital.

Picture copied from: http://airbreeze.com/index.php?q=land/how-it-works

Meteorological data and experience show, that often sunshine and wind are complimentary rather than corresponding with each other. That means on a sunny day, the sign of a more high pressure weather pattern, there is often not much wind and vice versa, due to the presence of different (high and lower) air pressure pattern and thus the occurrence of wind, clouds and less, or no, sunshine.

Thus, an installed solar PV system in a remote village without access to the national grid, to generate and store (in a battery bank) electricity, works well during sunshine hours but does not generate any power during the night and minimal power during cloudy or rainy days. On the other hand, a wind turbine can generate power whenever there is a minimal wind speed (usually about >3m/s wind speed, which is considered the “cut-in” wind speed when a WT’s blades start to turn and generate power), with increased power output (in the power of three!) the greater the wind velocity. Wind is often available during more cloudy days and often 24 hours a day.

Consequently, to tap into both, the available local solar AND wind energy resources, through a Solar Photovoltaic – Wind Turbine RAPS Hybrid System, allows an increased utilization of the local available RE resources, the “wealth” of a local community. With tapping into two (or in some cases even more) RE resources, we can create and enable a more sustainable energy generation solution.

RIDS-Nepal’s Prototype Solar PV – Wind Turbine RAPS Hybrid System

The following diagram shows the RIDS-Nepal Solar PV – WT RAPS Hybrid system configuration.

1) Solar PV Array 160 watt
Two polycrystalline solar PV module of each 80 watt are included in the solar PV array. The technical specifications are as following:

• Power Pmax: 80 W
• Open Curcuit Voltage Voc: 21.70 V
• Voltage and MPP, Vmpp: 17.20 V
• Short Circuit Current Isc: 5.20 A
• Current at MPP, Impp: 4.70 A

160 watt solar PV array 12VDC system, connected through a MPPT (maximum power point) charge controller, as hybrid system with the Air Breeze wind turbine, to the 200 Ah battery bank.

2) Air Breeze Wind Turbine 160 watt
The Air Breeze Wind Turbine has a maximum power output of 160 watt at 12.5 m/s wind speed. The following table shows the detailed technical specification of the Air Breeze WT.

3) Battery Bank
The battery bank consists of two, flooded lead acid, deep cycle Volta batteries, with each a capacity of 100Ah (C20 rating). They are connected in parallel to create a 12VDC solar PV – WT hybrid system. Thus the battery bank’s total capacity is 200Ah are connected in parallel. The voltage rating of the battery bank is 12VDC. The power coming from the wind and solar PV panels are both fed into the same battery bank. One 60 watt filament bulb is used as a continuous load.

12VDC x 200Ah capacity (at the C20 value) Battery Bank consisting of 2 x 100Ah 12VDC Volta, deep cycle, flooded lead –acid batteries.

4) DC to AC Inverter
The inverter converts the DC (Direct Current) power from the battery bank into sinusoidal AC (Alternating Current) to power the common electrical equipment we use on a daily basis, such as a PC, laptop, a light bulb, a TV, electrical kitchen equipment, etc. We use a pure sinusoidal inverter from the Swiss company Studer Innotec (http://studer-inno.com/) called AJ 275 (http://www.studer-innotec.com/upload/temp/Datasheet%20AJ%20series.pdf), with the following technical specifications:

• Brand name: AJ sinusoidal inverter
• Input voltage: 12VDC
• Output voltage: 230V/50Hz
• Output power: 275VA
• Continuous output power: 200VA

The AJ 275-S sinusoidal inverter converts the 12VDC power from the battery bank into 230VAC power to provide pure sinusoidal AC power for or RIDS-Nepal Kathmandu equipment, such as the PCs, laptops and office lights. The “S” version has also the option to connect a solar PV array of up to 10A current generation direct to the AJ275 inverter to charge the battery bank.

5) Data Monitoring System DT80
The data logger we use for detailed and accurate data monitoring is a DT80 (http://www.datataker.com/DT80.php) from the company dataTaker in Australia (http://www.datataker.com). The following parameters are measured, recorded and transferred according to a defined periodical time schedule by the dataTaker DT80 to the Internet server with the RIDS-Nepal databank:

• Solar PV voltage (direct connected and measured by the DT80)  
• Solar PV current (measured and converter to low voltage by a current transducer)  
• Solar PV power (DT80 internal calculated value) 
• Wind Turbine voltage (direct connected and measured by the DT80) 
• Wind Turbine current (measured and converter to low voltage by a current transducer) 
• Wind Turbine power (DT80 internal calculated value)  
• Load Voltage (direct connected and measured by the DT80) 
• Load Current (measured and converter to low voltage by a current transducer) 
• Load Power (DT80 internal calculated value)
• Battery Bank voltage (direct connected and measured by the DT80) 
• Battery Bank current IN and OUT (measured and converter to low voltage by a current transducer)
• Battery Bank temperature (direct connected and measured by the DT80 through a T-Type thermocouple)
• Ambient Air temperature (direct connected and measured by the DT80 through a T-Type thermocouple)
• Wind Speed (Anemometer (Vaisala WA15 http://www.vaisala.com/en/products/windsensors/Pages/WA15.aspx) impulse measurement direct connected and converted by the DT80)
• Global Solar Radiation (Pryanometer (ISET Sensor http://www.iks-photovoltaik.de/mess_und_prueftechnik/iset_sensor.php?lng=en) direct connected and the mV signal measured and converted by the DT80)

The DT80 dataTaker logger is the central unit to measure and record all the parameters we measure in the solar PV – WT hybrid RAPS system. The DT80 sends the recorded data on a periodical basis to the Internet server RIDS-Nepal databank (http://www.rids-nepal.org/databank) to follow continually the performance of the hybrid system.