Categories
Community Work Solar Energy

Unused Solar Panels – A Proposal

Introduction

We see solar panels installed at various places but not in use due to various reasons like

  • Cables broken
  • Battery not existing or damaged / end of life
  • Devices powered from the panels no more existing or damaged beyond repairs.
  • Few from the set of panels are damaged / glass broken.

These panels are in various sizes starting from as small as 20 watt to 250 or 300 watt per panel and in numbers ranging from 1 to 8 or 12 at any one given site.

Such installations are a common sight in rural areas, in form of Grampanchayat Solar Street Lights, and at Z P Schools where a battery based solar electric system was previously installed. Such ZP school systems, as far as we have seen, are in range of 1 to 2 KW solar panels capacity and provided with fairly large size batteries.

Besides providing power in case of outage of electricity from MSEDCL, these solar systems were seemingly intended to supply daily electricity to the school and in turn reduce the consumption and to lead to lower or zero bill charges every month.

Present Situation

At the ZP schools where a battery based solar system has been installed, most often, after 2-3 years if not less, the useful life of the original supplied battery has expired and there are no arrangements to procure a new set of batteries.

In such cases the existing battery can not store the electricity generated by the panels and thus the school has to consume electricity from the grid through the energy meter provided by MSEDCL.

The connection provided to ZP schools by MSEDCL often is set to have a tariff category named LT Public Services Govt. Education. This tariff category has a monthly fixed charge (स्थिर आकार ) of 343 INR, which means that even if there is no energy consumption in a month, the school needs to pay this much amount towards electricity bill every month.

To summarize, such schools do have solar panels and dead batteries and on the other hand end up paying electricity bill every month.

Most schools need to pay bill from their funds whatever available or rely on Grampanchayat team to pay the bills. It is more often meticulous followup and related hassles of potentially untimely payments, sometimes leading to disconnection of electric supply to the school.

Proposal

We propose that such sites are best suited for using the existing panels in a net metering arrangement with MSEDCL for the school.

We have carried out a survey to know what is the most important concern of the school teachers when it comes to electric supply, and below are the findings from schools in Murbad taluka of Thane district.

Survey Results

ConcernVotes
महावितरणकडून तांत्रिक
कामांमुळे/दोषामुळे
काही कालावधीसाठी
वीजपुरवठा खंडीत होणे
– ह्यापासून मुक्तता आवश्यक
6
वीजबिल भरण्याची अनियमितता,
कटकट, खिशाला कात्री,
निधीची कमतरता, बिल ना
भरल्यामुळे  वीजपुरवठा खंडीत
केला जाण्याची भिती 
– ह्यापासून मुक्तता आवश्यक
86
As can be seen the majority of survey participants have expressed an opinion that reduction in the monthly electric bills is more important.

Proposal Details

As a part of net metering arrangement, there is no need to install/maintain any batteries, electricity units generated from solar panels are used internally for school consumption and any excess are exported to electric grid.

The net metering approach involves following steps.

  1. Permission for Solar Net Metering installation is to be formally obtained from MSEDCL for the consumer number of the school, through the online application form, application fees 590 INR need to be paid.
  2. Existing solar panels are used to produce electricity.
  3. If needed, the support structure for the panels may have to be reconstructed, approx cost 10000 INR.
  4. DC electricity generated by panels is converted to AC power using a Solar Grid Tie Inverter, approx cost 23000 INR. The inverter is the only component that may need servicing in a very rare case, but comes with a 5 years warranty.
  5. A Generation meter is installed which records the electricity units produced by the solar panels. Approx cost 1200 INR.
  6. A Net meter is installed to measure the units Imported from and Exported to the MSEDCL grid, approx cost 2800 INR.
  7. Necessary safety devices (lightening arrestor, DCDB, ACDB, cables) are installed, approx cost 8000 INR
  8. Net Meter is provided to MSEDCL for testing, fees 590 INR
  9. Net Metering agreement as per standard content given by MSEDCL is prepared and printed on 200 INR stamp-paper to be handed over to MSEDCL.
  10. MSEDCL, after site inspection, will hook up the net meter replacing the old meter.
  11. Solar readings are then captured regularly by MSEDCL staff and billing as per the readings is initiated by MSEDCL as standard process.

As can be seen a total expenditure of about 45000 INR is necessary for a 2 KW system with existing panels to be put to use.

Benefits

  • Near 0 amount of monthly power bill and no more fear of power disconnection for school.
  • Utilization of an important asset which otherwise would have simply been a waste/idle, namely the solar panels.
  • Green energy initiative put to practice.
  • All of this for about 20+ years, thus saving money for the Grampanchayat.

Sample Installation

Starting in early 2021, and funded by Malati Vaidya Smruti Trust, a solar net metering installation has been successfully completed for consumer number 019000002570, Z.P. School, Milhe, Mhasa Dhasai Road, Murbad.

2 KW old panels were available from a not-in-use solar pump in custody of the Grampanchayat, who handed over the panels to school for the solar net metering project.

Just rececntly solar billing has started and school is seeing excess units exported to MSEDCL, these will be converted to monetary credit in the electricity bill for the school in month of March or April. Thereafter the credit amount will get utilized to pay off for the monthly fixed charges of subsequent months.

Request For Support

We seek contributors and donors to fund such projects and thus put to use the idling infrastructure (mainly the solar panels) and help the schools reduce their electric bills as much as possible.

Thank you.

https://www.pbodas.in/

Categories
DIY Energy Saving Environment Solar Energy Water

Skid Mounted Mini Pump

For irrigation of small farms where water source is available nearby (either an open well, pond, lake or any such water body) it is possible to use small pumps and operate them on solar panels.

These pumps are easily available at reasonable prices online as well as in local market in most of the cities and small towns accessible to farmers. They are used very commonly in battery operated backpack sprayers used for pesticides.

This post explains some important aspects of this type of pumps for use at small irrigation sites.

Such a pump is run by a DC motor and has a PVC block head where positive displacement of water is achieved by action of miniaturized pistons inside the block.

A pump having single motor is often priced at 550 to 650 INR and delivers upto 3 LPM water and claims to generate pressure of 70 PSI or 5 Bar i.e. upto 50 meters of height.

Pump with twin motor is also available and priced at 1000 INR, delivers 5 to 6 LPM of water at similar pressure.

Next two images show a single motor and dual or twin motor pump.

The DC Motor used is a DC motor with brushes and follows a standard specification named as 775 motor, some details can be found here.

https://somanytech.com/what-is-775-motor/

The motor can be operated over a wide range of DC supply voltage (6 to 36VDC) but the pump manufacturers normally mark the pump for operation in range of 12 to 14.5 VDC only.

We have installed such pumps at a couple of sites and safely connected to solar panels of 12VDC nominal (or 18VDC MPPT voltage). The motor of the pump nicely works with the electricity generated by solar panel during the daytime. As the intensity of sunlight changes throughout the day, the output flow of water varies and is acceptable for the irrigation purposes.

Inlet and outlet of the pump is however a non-standard (or at least not easily available) tubing size. Most suppliers provide a PVC/HDPE tube with threaded PVC nut to attach to the pump outlet nozzle, but the connectors with standard pipe sizes (say 0.5 or 1 inch nominal bore pipe) are difficult to find.

We have used a typical nozzle connection seen in pictures and created a simple skid mounted assembly of this type of pumps, eiether one pump on the skid or 2 on the skid as per the requirements.

With 2 pumps on the skid it is seen that 150 to 200 watt panels are adequate for operation throughout the day. For single pump a panel of 75 to 100 watt is appropriate.

Next few images explain the mounting approach we have used and is only a suggestion. Any suitable alternative can be followed that meets the needs and materials availability at the installation site.

Single Pump Skid

Dual Pump Skid

Front view of the pump skid with inlet and outlet pipes on left side.

Seen from top at an angle / 3-D view.

Left Side View

Rear View

Right Side View

Top View

Important Instructions

  • Pump and motor must never be submerged in water and water must not get into the motor.
  • DC power supply polarity needs to be correctly followed. Green wires to be connected to negative terminal of the battery or solar panels, and red wire to positive terminal.
  • DC supply voltage must never exceed 18 volts.
  • In no case, AC supply / mains supply shall be applied to the motor, it is hazardous besides the fact that it will permanently damage the motor.
  • Testing of pump without water by supplying DC power for a second or say two seconds is ok, but must not run the motor for longer duration without water.
  • At the inlet pipe a suitable filter in form of nylon mesh is highly recommended. The internal piston mechanism of the pump is too small to get clogged by smallest of the particles.
  • This type of pump can generally start from dry run and can self prime in a few seconds, but if it does not do so, please do not run it dry for long time. Instead open the nozzles and check if any clogging or blockages. Try to pull water from outlet nozzle or pipe by sucking the air.
  • The pump can lift water from upto 5-6 feet on the suction side, however it is better to keep the suction pipe length as small as possible.
  • It is recommended to install a footvalve at end of the suction pipe submerged inside the water, it is best to attach a filter mesh around the footvalve.
  • Make sure that the pump skid is mounted on a sturdy platform or base. Alternatively pump can be suspeneded firmly inside an openwell clearly above the water level.
  • Use solar panels of 12VDC nominal voltage only, any higher voltage panels if connected to the pump will damage the same. It is better to first check the nameplate on the backside of the solar panel before connecting for the first time. The nameplate should read 12VDC nominal and/or 17-18 VDC MPPT or maximum power voltage.
  • Single pump skid is suitable to operate with 75 to 100 Watt panel and dual pump skid with 150 to 200 Watts. Excessively higher wattage of the solar panels must be avoided.
  • This type of pump is supposed to be used for intermittent duty only however through our experimentation in actual sites, we find that using the pump every day for 3 to 5 hours is fine.
  • Connect the outlet pipe with suitable coupling or union with the delivery pipe to be arranged at the site to suit the distance of the final delivery location away from the water source.
  • Ensure that the inlet and outlet pipe connections do not lead to forces on the pipes or the skid.
  • If in doubt please reach out to us through email or phone.
Demonstration of 3 pumps at a site in murbad

Thank You.