The Tier Solar Controller

Local electricity generation is one of the key challenges of technology for developing regions. Although we were driven by the need to power rural connectivity solutions, the solar controller described here makes sense for any remote ICT project with power needs up to about 100W, which includes most home solar systems, as well as single PC projects, such as kiosks. The intended use of this board to provide reliable electricity for our WiFi-based longdistance (WiLD) links, particularly relay points. The relay point may be in the middle of a remote area where no grid power is available. Furthermore, even in areas served by the grid, power is often unreliable. To address the issue of providing power to the wireless routers, we focus on solar power. Depending on the situation, solar power can be the only source of power or can complement existing power from the grid. The main components of a solar power setup (solar panel, battery and charge controller) are readily available, and can be used to supply power for wireless routers. However, current designs did not meet our goals in terms of cost, ease of use, and remote monitoring. With current available technologies, one has to put together several pieces of hardware to come up with solar power setup for wireless routers. Having several individual pieces of hardware for a setup increases the complexity and expense of the setup. Ideally, setups should have the least components from an ease of use and cost standpoint. The solution presented here combines the peak-power tracker (PPT), the charge controller, power of ethernet (PoE), and remote monitoring into one small board, with a single unit cost of US$50 (so far). In addition to reduced cost, this board is very easy to use: just connect the panel and the battery, and the power flow out the PoE port to the wireless router. Using the ethernet port, we can query the status of the panel and the battery for remote monitoring. Finally, the board pays for itself! First, the peak power tracker achieves about 15% more power out of the solar panel (compared to a direct connection). Second, the charge controller should roughly double the lifetime of the battery, by ensuring proper charging and discharging. In addtion to the financial benefits, doubling the battery life halves the considerable health and environmental problems of lead-acid batteries. We next present the design, following by details on its capabilities and limitations.