Project Everest

[Solution]: Solar Consulting - Pico-Solar - Malawi July 2018

Introduction:

The proxy product the energy team has been using in July had features and problems that the July team was not satisfied with. In particular, the AC charger and the lead-acid battery of the GDLite were identified as areas that need to change; This is due to the risk of overcharging when charged through an AC connection. The desire to change from lead-acid to lithium-ion is driven by the short lifespan of lead-acid batteries as discussed in a previous post. The product should power three globes for a minimum of 6 hours consistently from a single charge as well as be able to charge a phone. The case should be sturdy with a handle for ease of carrying. A negative impact that must be considered before design begins is the lifecycle of the product. It is PEV’s responsibility to design a product and set in place systems that ensure the proper disposal of broken units. Photovoltaic waste is becoming a significant problem within Sub-Saharan Africa in particular from non-branded solar products. An overview of best practice from UCSC and the University of Edinburgh can be found below. The webpage has links to organisations that advise solar companies the best practice when designing pico solar products.

https://slab.sites.ucsc.edu/pico-solar-scorecard/

Current Specs:

Lights:

3x 3W LED globes

  • Eight LEDs each globe
  • Each globe output 120LM
  • Colour temp 6500-7000K

3x 5m insulated cables

These light globes should be able to be plugged and unplugged from the central battery unit; this is to allow for a modular system and adjust for the number of rooms. The cables and lights should also be water resistant to account for leaky roofs and safety. 120 Lumen output is the output of the GDLite product and has so far been considered sufficient for lighting needs. The colour temp of 6500-7000K is a white light that is both impressive to villagers who are used to candlelight and useful for both studying and cooking. 5m cables are recommended for use because the lights can be used in different rooms, but this may be increased if the demand is high for a longer cable. One of the suggestions made to the team by an electrical engineer was to move the position of the light switch closer to the unit. To allow for the lights to be hung from the ceiling and still used.

USB output:

1x 5V 0.5A USB output CCCV

1x multi-lead charger cable

  • Mini USB
  • Micro USB
  • Nokia 3.5mm Pin
  • Nokia 2mm Pin
  • 5mm Pin with no centre pin

5V 0.5A output for USB chargers is standard. The multi-lead charger with a selection of male pins has been chosen with its array of pins due to the popularity of these ports within Malawi. The charger cable should be able to charge multiple devices from a single USB port.

CCCV stands for Constant Current Constant Voltage; this means that the initial charge will be a constant current, this allows the battery to charge quickly; after the battery is charged to the voltage requirement the charger switches to constant voltage and begins to reduce until the battery is full slowly. This CCCV method is why the first 80% of a modern phone will charge quickly, and the last 20% will charge much slower.

 Battery:

1x 24 Wh lithium-ion battery

Currently, the GDLite proxy product contains a 24Wh lead acid battery. For future iterations, this should be changed to a lithium-ion battery of similar size as discussed here. Size may increase if high enough demand is found. Recommended material is LiFePO4.

Solar panel:

1x 7Wh polycrystalline photovoltaic panel at 9V

1x 3m insulated cable

The 7Wh polycrystalline panel is more capable than GDLite ships with, but feedback from customers in Nancholi has prompted the increased panel wattage. The 3m long cable is to allow the panel to be outside while the central battery unit remains inside. The cable, solar panel and their connection should be waterproof so the panel can be left outside, rather than requiring the customer to take the panel inside if it rains. Feedback has shown that customers do not place the panel outside unless it is sunny, this then decreases the amount of power gained.

edited on 13th September 2018, 00:09 by Justin Hakeem

Andrew Vild Aug 10, 2018

Status label added: Solution

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Ella Grier Jan 6, 2019

Status label removed: Solution

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