Part: 1 - Solar PV Electric Operations


Shared on August 31, 2012 written by Keith McRae

Operating Wireless Gateways & Cellular Routers Off-Grid with Solar PV Electric

Part 1: Core Elements of a Solar Power Wireless Router System

The intelligent wireless gateway and router, often referred to as a wireless modem, is perfect for connecting where there is no wireline data available. Therefore it is logical to connect the wireless wide area network modem where there is no grid electric readily available as well. The solution is to harvest energy from the sun using solar photovoltaic cells. Wireless gateways use very small amounts of electricity, and they often run on DC power, the same direct current electric we can generate from solar PV arrays. USAT architects and assembles single panel systems designed to use a pole mounted panel, a NEMA enclosure, and a battery array to power a wireless modem and connected equipment.

It is important to consider what equipment will be attached along with the wireless modem/intelligent gateway. Consult with your USAT sales representative before selecting attached equipment as disparate voltages, native AC powered devices, and high draw equipment can force the solar assembly to be oversized and cost prohibitive. For example, if you need to attach an IP Pan-Tilt-Zoom camera to the off-grid system, USAT can suggest low current PTZ cameras that work well with solar assemblies. A similar example is with network switches. Switches designed for 12Vdc or 24Vdc or POE systems should be selected, and these should be rated for a broad operating temperature, for example -40C to +60C.

Calculating modem power demand is based on measuring the known power consumption characteristics of the gateway. These can be broken down into power demands for four states: Transmit, Receive, Idle, and Power Save. USAT examines data usage, keep alive pings, and other modem activity to calculate the daily consumption and a variance factor to create both the maximum demand and the average the modem will have. USAT has modeled modem power consumption characteristics for many makes of wireless equipment including the Sierra Wireless Airlink Raven, Sierra Wireless Airlink PinPoint, Sierra Wireless Airlink GX-400, Sierra Wireless Airlink GX-440, Encore Bandits, Cradlepoint COR and MBR, Digi Connect, Digi WR, and Digi Transport, CalAMP, Multitech and Red Lion Sixnet Bluetree. Wireless modules designed for Sprint's network varies in energy consumption from T-Mobile's and AT&T's network which varies in energy consumption from Verizon's network. Likewise we need to explore whether the modem will be on GPRS, HSDPA, HSUPA, or 1x-RTT, or EVDO rev A or 0. Likewise 4G presents different module consumptions whether running LTE, or WiMAX, or one of the HSPA+ variants. Each device has unique power requirements, and these all vary based on the intended application. Let USAT size the system for you leveraging our engineering expertise specific to solar and wireless data applications.

The core elements of an off-grid solar photovoltaic system are as follows:

These core elements will be broken and discussed in more detail out in subsequent posts.

Continue reading Part 2: Solar PV Electric Operations of the full article.

Keywords: Solar PV, Solar PV Operations, Off-Grid Solar PV

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