DESIGN, INSTALLATION AND MAINTENANCE OF SOLAR HOME SYSTEMS IN RURAL AREAS

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1 DESIGN, INSTALLATION AND MAINTENANCE OF SOLAR HOME SYSTEMS IN RURAL AREAS by Matimba Mathebula, Xahumba Engineering Consulting X ahumba Engineering Consulting (Pty) Ltd is embarking upon a journey of ensuring that South Africans use alternative energy sources. As the entire globe is going green and moving away from the use of fossil fuels for power generation, households from different local municipalities across South Africa are benefiting from the Non-Grid Electrification Programme initiated by the South African Government. The government through the Department of Energy identified high number of households in South Africa that are still living without electricity and decided to close the gap by using a solar home systems (SHS) technology as one of the solutions. SHS are installed in rural communities where there is unavailability of networks, infrastructure and where the topography is unsuitable for grid connections. Solar systems produce electricity for free using the sun radiations. The system is clean, and it is the fastest and shortest way of running away from electricity tariff hikes. Beside its advantages of producing power for free from the sun and contribution to keeping the environment clean, the system also assists in saving water which is a scares resource in South Africa. Approximately 1.28 kilolitres of water are used to generate 1MW [3]; therefore, that amount of water is saved from every 1MW produced by a solar system. Looking at the crises of water in South Africa, solar system is one of the alternatives to resolve that. Xahumba Engineering Consulting (XEC) has been appointed by the Department of Energy to provide the design, installation and maintenance of SHS. A statement on the Engineering News article titled BEYOND THE GRID indicates that households have been connected through the nongrid technology since 1994 [4]. Of those solar home systems, XEC, together with its partners, has installed systems between March 2015 and May 2018 and is currently responsible for maintenance thereof. XEC conducts the designs, installations and maintenance of SHS as per the required standards; SANS 959-1/NRS052-1, SANS 959-3/NRS052-3, SANS Design:- XEC designed the SHS with a core objective of meeting the Client specifications as outlined below. Qualified and experienced personnel were deployed to ensure that the systems were designed beyond the expectations of the clients and all stakeholders involved. The systems complimented the client s specifications, met the needs of beneficiaries, and answered the call of technology improvement. Client specification: The following are the minimum specification from the Client:- Minimum of 95Wp solar system Minimum battery size of 96Ah, 12V System to supply maximum of eight lights of 3W each (six interior and two exterior) Beneficiary to be able to connect DC TV, Radio, DSTV and phone charger. Considerations: Below are the considerations by XEC design team: - Battery to last for at least 2 days without recharging from the solar panel. Solar panel to operate effectively at local temperatures and produce enough power to charge the battery 5W lights to be used outside instead of 3W. 3W is not bright enough. Recommended 80% battery s depth of discharge (DoD). System losses shall be catered for. Beneficiaries safety.

2 The specifications set by the Client and considerations by XEC were then consolidated into one to design a very effective and reliable SHS. Energy Required: A first question that comes to one s mind before designing a SHS is what is it or which appliances the system should be designed to cater for? Then after answering that question work out on the amount of minimum power required by the appliances to function effectively. XEC designed the systems with assumptions that the 12V DC appliances mentioned below shall be catered for: APPLIANCES POWER Description Power (W) Quantity Hours (h) Total Power (W) Watt-Hour (Wh) Interior Lights Exterior Lights TV Radio DSTV-Decoder Phone Charger Total Table 1: Appliances Power Table 1 above shows that the minimum solar panel output should be 93Wp, a 100W polycrystalline solar panel has been selected to be installed per household. The motive behind selecting a solar panel with more rated power than required is because it is highly impossible for a system to operate without losses in real world; therefore, the extra power is there to cater for those losses. Solar panel performance at local temperature: Ambient temperature has effect on solar panel s temperature and output performance; rise in ambient temperature increases the solar panel temperature and reduces its output voltage [1]. XEC retrieved temperature history of the Eastern Cape and checked if the selected solar panel would operate effectively under the province s worst temperature conditions. The lowest and highest local temperatures ever experienced by the Eastern Cape (-18 C on the 3 rd of November 1918 and 50 C on the 28 th of June 1996) and the solar panel information in table 2 have been used for calculations. Description Max power (Pmax) 100W Max power voltage (Vmpp) 18.8V Max power current (Imp) 5.51A Open circuit voltage (Voc) 22.1V Short circuit current (Isc) 6.04A Cells Polycrystalline Number of cells 36 Temperature Coefficient Isc Voc Pmax %/ C -0.31%/ C -0.41%/ C Temperature at Standard Test Condition (STC) 25 C Nominal Operating Cell Temperature (NOCT) 45 C Table 2: Chosen Solar Panel Specification at Standard Test Conditions Each degree rise in temperature above 25 C, the selected panel short-circuit current decays by 0.051%, open-circuit voltage by 0.31%, and maximum power by 0.41%. Solar panels are tested under laboratory conditions, called Standard Test Conditions: at an Irradiance (light) level of 1000W/m2 with a temperature of 25 C. But in the real world these conditions are constantly changing so the panel output is different from the lab conditions. V OC_maximum = (T Local_Minimum + TSC) V oc(temperature coefficient) 100 = ( 18 25) ( ) = 21.73V + Voc

3 V OC_minimum = (T Local_maximum + NOCT TSC) V oc(temperature coefficient) + Vmpp 100 = ( ) ( ) = 18.58V The formulae used above do not take humidity into consideration and it is proven that it also affects the performance of the solar panel. Humidity effects the performance of the solar panel and proves out to decrease the produced power up to 15-30% [2]. If the humidity does not change drastically, the solar panel s open-circuit voltage, based on the calculations above, would be expected to range between 18.58V and 21.73V provided the temperature is between -18 and 50 degrees Celsius. Required battery watt-hours: Solar panels produce less or no power during rainy or overcast days due to minimal radiation they receive from the sun. Therefore, this situation also had to be taken into consideration when designing the SHS by ensuring that a selected battery can provide the required minimum power to the connected appliances for certain number of hours or days without being recharged by the solar panel. However, the solution is only temporal, and the system will still be affected if the bad weather conditions persist for more days than anticipated. The required battery watt-hours are calculated using the days of autonomy mentioned under design considerations, recommended depth of discharge and appliances total watt-hours. Days of autonomy = 2 = Battery Watt_hours = 1230 Battery Amp_hours = Where Battery Voltage = 12V Battery Watt_hours Depth of Discharge Appliances Watt_hours Battery Watt_hours = Battery Watt_hours 0.8 Battery Amp_hours = 1230Wh 12V Battery Watt_hours Battery Voltage = 102.5Ah Guided by the calculation above, a 102Ah, 12V battery was selected to achieve the required 2 days of autonomy. If the system is not abused and used as per the assumptions in table 1, households will have enough power from the battery to last for at least two days without being recharged during rainy or overcast days. Battery charging hours: It is also imperative to ensure that the solar panel has a capacity to fully recharge the selected battery. This is done by checking how long it will take for a battery to be fully recharged assuming the solar panel is operating at its maximum and no other load is consuming power from the solar panel. The calculations below have been conducted using the worst scenario where a battery is 100% discharged. Solar Panel Maximum Current = = Solar Panel Power System Voltage = 8.33A Hours Required to fully recharge the battery = = Battery Amp hour DoD Solar Panel Maximum Current 102Ah 100% 8.33 = 12.24h

4 CHARHING HOURS (H) Therefore, the battery requires about 12 hours (approximately 2 days) to fully recharge when it is 100% discharged BATTERY DOD VS CHARGING HOURS DEPTH OF DISCHARGE (%) Figure 1: DOD VS Charging Hours Figure 1 above shows that the hours in which the battery takes to full recharge is directly proportional to the DoD. Other designs conclusions: The specifications, considerations, assumptions and calculations above also assisted XEC to select other components required to complete the system. Charge controller - A 10A,12V charge controller has been selected guided by the system maximum current of 8.33A. Cables - 2.5mm 2 from the solar panel to the charge controller and to connect from one house to the other. 4mm 2 from the battery to the charge controller. 2.5mm 2 from the charge controller to the DC box. 1.5mm 2 from the charge controller to the lights. The selected cables were a bit oversized to accommodate system losses. Beneficiary safety: XEC has a culture of always putting the lives and well-being of people first, and do not compromise when it comes to safety. SHS had to be designed in a way that it never and will never in any way endanger the lives of beneficiaries, provided the systems are not abused. The following measures were implemented to ensure that the systems are safe to use: Cables channelled through trunkings. Joints covered using insulation tapes and where possible put inside a trunking. Batteries installed inside battery boxes. Seals used to lock the battery boxes. Design Summary After all the assumptions, considerations and calculations, XEC ended up with the following final design: 100Wp Solar panel, 102Ah Lead-Acid Battery, 10A Charge Controller, 3W LED internal lights 5W LED external lights DC output to accommodate DC TV, Radio and DSTV decoder

5 Figure 2: SHS Wiring Diagram Installation More than 10 installation teams were deployed to conduct the installations, and each team consisted of a skilled, semiskilled and unskilled personnel. Local labourers were also among the teams. Before the installation process commenced, XEC came up with mitigations to deal with the potential risks that were identified as threats to the project. The threats included but not limited to those in table 4 below: Risk/Threats Impact Mitigation No easily accessible More time is spent on Arrange with beneficiaries to roads delivering material to collect material from a neutral beneficiaries. point. Cracked walls It puts the lives of workers in danger as the walls could collapse while they re busy with the installations. Beneficiaries might sue XEC for cracked walls, as they can claim that the walls cracked during the installation process. Shading Solar panel produces less or no power due to shading. Home owners not available Community members attacking technicians Disturbance of the installation schedule. Delay of the project Injuries and/or loss of lives Loss of trust and sound workmanship Technicians must avoid climbing on cracked walls. Take pictures of the cracked walls before the installation process. Beneficiaries must sign a declaration form declaring that the wall was already cracked before installations. Install solar panels where it will get enough radiation from the sun. If there is no other perfect spot where a solar panel can be installed, arrange for the tree/s to be cut down if the shading is caused by trees. Share installation schedules with ward committees. Word of mouth is very powerful in rural areas; therefore, spread out a word one or two days in advance. Always have local labourer/s on site.

6 CURRENT (A) Table 3: Identified Threats, Impacts and Mitigations Ward committees to appoint someone among themselves to accompany installation technicians. Beside conducting a proper planning to avoid and/or reduce the risks in table 3, XEC provided a detailed training to all the teams prior to installations to ensure that everyone was equipped with relevant skills. Issues of safety and quality were also dealt with during the training. For quality measures, one SHS was installed in the presence of all teams and used as a standard system. Materials were inspected prior to installation to certify that only quality is provided to the people. After the training and material inspections, teams were then provided with relevant personal protective equipment and tools, then deployed to different sites to conduct the installations. Installation teams were working on a daily target to guarantee that a deadline set by the client was not compromised, and each team was installing a minimum of five houses a day. The teams worked beyond expectations, and even compromised their times in the name of delivering on time. However, quality was never sacrificed along the process. Tests The following tests were conducted in a workshop. Tests could not be conducted on site because it would not be easy for XEC to monitor the systems and guarantee that the households do not meddle with the tests. To compare apples with apples, only lights were connected as the only loads. EXPECTED VS ACTUAL CURRENT Expected Measured LIGHTS POWER(W) Figure 3: System's Expected and Actual Currents The results in figure 3 shows actual current lagging behind the calculated values. The difference is due to factors like voltage drops and efficiency of the systems. Current measuring instrument for actual readings were connected between the charge controller and the load (in series with the load).

7 VOLTAGE (V) NUMBER OF HOURS BATTERY OPERATING HOURS LIGHTS POWER (W) Expected Actual Figure 4: Battery Operating Hours The tests in figure 4 above were conducted to check the reliability of the selected batteries. The expected hours were calculated by dividing the battery size (Ah) by the expected system currents on different loads. To obtain actual hours, batteries were first fully charged, then connected to the maximum load through a charge controller and switched on to run continuously until batteries reach 100% DoD and switch off SOLAR PANEL VOLTAGE VS TEMPERATURE TEMPERATURE ( O C) Figure 5: Solar Panel Open-Circuit Voltage The open-circuit voltages in figure 5 were measured directly from the solar panel s terminals under different temperatures. The measured voltages are within the expected range (18.58V and 21.73V), which clearly indicate that humidity was not putting pressure on the systems. Maintenance Sooner or later, all systems tend to malfunction, and nothing can be done to stop that from occurring. Maintenance is the only technique that can be used to control the systems performances. XEC had to set up an office in the Municipality where the systems where installed and put a system in place that specifically deals with maintenance of SHS. There are four maintenance teams at different locations which are always on standby and ready to serve people.

8 All beneficiaries were provided with unique numbers during the installation stage. The unique numbers and beneficiaries information are kept in the maintenance database. A beneficiary would only be requested to provide the unique number when calling for assistance. When the unique number is punched onto the system, all beneficiary s information including full name, ID number, location and status are pulled out of the system. The beneficiary will then be required to verity his/her ID number and location to ensure maintenance personnel are set to the correct location. After that a job order is created and assigned to the maintenance team closer to the location and expected to report back within 24 hours. The following challenges are experienced on site. Beneficiaries disconnecting the systems Illegal connections Stolen systems Conclusion XEC has installed systems in various municipalities across the country between August 2015 and March 2018 as part of the non-grid electrification initiated by the South African Government through the department of Energy. The SHS designed and installed by XEC meets both the minimum specifications by the Client and the user requirements. The system provides basic electricity to rural households including lighting, use of television, radio and cell phone charging. The installation of SHS in South Africa has proven to be very helpful and should continue until all households have access to basic electricity. The improvement of the systems and technology should however continue even when all households are reached. The installation of SHS restores dignity in rural communities and gives people a feeling that the government did not abandon them. The implementation of SHS creates jobs and reduces the number of service delivery protests. School children from communities that have benefited from the programme thus far have adequate light environment to study and families are no longer dependant on candles or paraffin lamps. Eliminating the use of candles/paraffin lamps reduces the loss of lives that were caused by these unsafe sources. Also, uncofirmed reports indicate that the learners whose households have benefitted from the programme are performing better at schools. XEC commend the South Africa Government for initiating the programme of this nature and encourages the government to make Solar power an intergral part of the energy mix in South Africa. Beside residential installations, XEC also do commercial ground mounted, rooftops and car ports solar systems installations. Recommendations The South African Government should consider increasing the size of solar home systems and make a provision for inverters. Households end up doing illegal connections simply because they want to connect AC appliances which is impossible on the DC systems. Local municipalities should uplift rural communities by making sure that 50% of maintenance work is shared among local small enterprises. Service providers should be given a mandate to properly train local enterprises about systems and maintenance. Local Municiaplities should increase their participation in the programme and also support the Service Providers by identifying areas that needs the services and timeously providing the necessary information when required. References 1. A.R. Amelia, Y.M. Irwan, W.Z. Leow, M Irwanto, I. Safwati, M. Zhafarina, 2016, Investigation of the Effect Temperature on Photovoltaic (PV) Panel Output Performance, International Journal on Advanced Science Engineering Information Technology, Vol.6. No.5 2. Manoj Kumar Panjwani, Dr. Ghous Bukshsh Narejo, 2014, Effect of Humidity on the Efficiency of Solar Cell (photovoltaic), International Journal of Engineering Research and General Science, Volume 2, Issue 4

9 3. Eskom s integrated report, 31 March 2018, Accessed: 2018, September Schalk Burger, 19 June 2018, BEYOND THE GRID, Accessed: 2018, September 27 Author Matimba Mathebula, B-Tech Electrical Eng. Cell: Contact Max Chauke Pr. Eng Tel: Company: Xahumba Engineering Consulting (Pty) Ltd admin@xahumba.co.za Website: