Sustainable Opportunities Ltd

Greening Urban Evironments

Guidelines - Project Four

Portable Solar Power System

The objective of this project was to produce a simple small portable solar power system which can be used to power all sorts of small electronic devices (at USB 5 volts) and other devices (e.g. LED lights, irrigation valves) at 12 volts. A solar regulator takes the output from a solar panel to control the charging of a battery, but also provides a 5 volt and a 12 volt output for powering a range of useful GutterGrowing devices.

The solar power unit packs into an easily carriable waterproof transparent container so that it can be moved to any location where small amounts of 5 volt and 12 volt power are required.

What you need:

  1. Small 12v solar panel
  2. Small 12v sealed rechargable battery (normally lead acid)
  3. Solar regulator with 12v and 5v (USB type) output
  4. See through waterproof carry container with lid

WARNING

The following details are provided as GUIDELINES ONLY. There are vast ranges of all the components needed for this project and the choices will depend on individual requirements. The illustrations provided are for a working experimental system we have under test and are not intended to be prescriptive. Individuals MUST ensure that their choice of components fit together and are compatible with each other.

The choice of physical size of the container and solar panel is very much an individual choice. Vendors of solar panels and controllers will be able to advise on suitability and compatibility with various sizes of battery. Vendors will also be able to provide connection wireing suitable for your choice of components.

Step 1 Choose a small solar panel and a transparent container

There are many options on the market for the choice of a small solar panel - the one shown here is a 10 watt solar panel which measures 38cm x 25cm. There are also many options for choice of transparent containers - the one shown here is a 25 litre plastic storage box from Wilco which measures 32x40x25 cm. It has moulded in carry handles (useful) with a ridged top surface in the handle area (very useful for guiding power leads running out of the system). It has a transparent lid which when in position retains, and keeps dry, all the components.

It is important to check the dimensions of all the components to ensure they fit into the closed container. Our 10watt panel costs around £20-£30 and the container another £5

solar panel battery solar controller

Step 2 Choose a small 12v rechargable battery

Typically a small 12v sealed lead acid rechargable battery will be the best choice. The one shown here is a Yuasa 7Ah 12v sealed lead acid rechargable battery (cost £12-£16).

Step 3 Choose a 12v solar battery charge controller with 5v and 12v outputs

solar controller

Our chosen controller has a display which shows the battery voltage. The connection points along the bottom provide connections to the solar panel and to the battery. Usually it is important to connect to the battery first and then secondly to the solar panel. Down the right side there are two USB output connectors providing 5v and two output connectors providing 12v (cost around £15).

We have been using it to run an arduino microcontroller and relays (at 5v) which control 12v irrigation valves (details coming soon) . It also runs a music player which cheers everyone up when we hear what Donald Trump is up to.

system in boxsystem in portable boxperson carrying solar system

The whole system packs into an easy to carry box so that you can site it or move it to any convenient space. The solar panel is waterproof and so it can be used (for very limited solar capture) in the container - or more normally outside the container where it can be situated to maximise solar capture.

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