To understand the various configurations for solar power, we will cover a few different applications.

Characteristics:

Peak operation during summer and middle of the day

Special inverter can add AC power

Ventilation fans

Water pumping

A stand-alone system is shown in Figure 9-8.

Battery storage allows operation at night or during bad weather

Charge regulator prevents battery from over-charging and over-discharging

System controls can include circuit protection and remote monitoring

Inverter can add AC power

Telecommunications telemetry

Outdoor lighting

RV or boat electric power source

Remote homes or storage facilities

There are also a number of hybrid systems.

Generator plus rectifier allows battery charging for full energy availability in any climate or season

Generator can be multifuel source (natural gas, diesel, propane)

AC bus allows direct AC power to loads from generator through transfer switch, while also recharging the battery through the rectifier

DC Bus has all power flowing through battery (DC), avoiding complex transfer switching and any anomalies in the power load

Large telecommunications stations

RV with generator

The wireless repeater in this chapter will be designed using the stand-alone model.

The heart of the system is the solar panel, while the body is the enclosure cabinet. The enclosure will house all of the electronics and keep them safe from the weather and other predators. The enclosure will be directly connected to the solar panel and wireless antennas. Flexible conduit is recommended for the solar panel junction box interface, while Times Microwave LMR-400 cabling is suitable for the antenna connections. If your enclosure has “knockouts” for conduit, so much the better; otherwise, drill out the holes for your pigtails and electrical conduit.

Figure 9-9 shows the enclosure layout. Components are spaced evenly for ease of maintenance. Electrical wiring exits the enclosure on the left. Antenna cabling exits on the right through bulkhead pigtail connectors connected to LMR-400 cable.

Since this system is to be deployed in an outside remote location, it is recommended that you first unpack all of your items indoors to ensure that you have all the required pieces and that they are all in good condition prior to beginning.

In addition, you may want to build as much of the control cabinet as possible before deployment to test components and minimize the number of total items that will eventually be carried to your destination.

It is critical to closely inspect your PV panel, because it may be the most fragile and valuable part of this configuration. Specifically, look for any cracks or breaks in the glass or framing that may have occurred during the shipping process. If you notice any irregularities, contact your dealer for immediate replacement. Once you are satisfied that all the contents are present and in reasonable condition, you are ready to begin.

You should start by assembling the contents of the control cabinet first. This is due to its complexity, and it is the core of your system. Once all of the items are mounted and wired into the cabinet, the balance of the installation will require little more than erecting the pole, mounting the PV panel, control box, and antennas to the pole, and then testing. Figure 9-10 shows a diagram of the cabinet layout for this installation.

For ease of installation, and to simplify future maintenance requirements, various lengths of Velcro Strips are part of the list of materials. This Velcro will be used in place of drilling, nuts and bolts. Moreover, this approach will eliminate the need to punch holes into your control cabinet which could later result in problems from leakage.

Refer to your internal cabinet diagram for component orientation and organization. You may choose to design your cabinet differently, and that is fine, just ensure that you have a proper cable management plan before you get too far into the project. This is extremely important in future days and weeks when maintenance procedures may be required and taking parts in and out could be hampered by inefficient arrangements. Figure 9-12 shows the charge controller in place. Substantial Velcro adhesive holds the charge controller in place.

The DC-to-AC inverter converts the DC battery power into AC power for the power strip and wireless components. The battery directly connects to the DC inputs on the inverter. Figure 9-14 shows the inverter installed and connected to the battery.

By choosing to use an inverter to provide universal AC power, you have the option of easily changing out radio equipment. Also, while on-site at the repeater system, extra AC power comes in handy.

When choosing a DC-to-AC inverter, a low-cost “modified sine wave” inverter works fine with this type of equipment. However, parasitic power is a factor. Try to find an inverter with low internal current consumption. Anything with less than 0.2 A (200 mA) is fine.

As you may have noticed, the charge controller and the inverter are both connected to the battery. Solar energy is used to charge the battery via the controller, while simultaneously, the inverter pulls electricity out of the battery for the wireless radios.

The wireless equipment will be stacked with the access point on top of the bridge, so keep that in mind as you begin to install this component. Additionally, the radios will be AC-powered devices, and you will need to route the power cords so that they can cleanly access the power strip that will be mounted shortly.

You will clearly need to modify this step if your product is a single-board computer with integrated radios, like a Soekris or open brick computer described in Chapter 8.

The installation of a power strip will add enormous convenience and flexibility in your system. Not only will it be responsible for supplying power to your critical communications devices, but it will also give you the ability to serve any other electronic device that meets the output requirements this system has been designed for.

For instance, you will be able to operate low power tools, temporary lighting, cell phone and laptop chargers and any other AC-powered convenience devices that may become useful during the installation.

Your AC Power Strip will be mounted to the top of the cabinet (see Figure 9-16).We recommend attaching it the way you did all the other devices, with Velcro as the primary fastener. Adding a third strip of Velcro to the middle of the AC Power Strip and to the corresponding place on the cabinet back wall will add stability since this device will be subject to more strain from plugs being inserted and removed. You are certainly welcome to use two-sided tape, but we don’t recommend drilling holes through the exterior of the cabinet. Any water leakage in this area could be hazardous to the equipment.

At this point, your cabinet should be fully populated. Charge the batteries by using a 12-volt power source attached to the leads of the charge controller. Anything supporting a few amperes at 12 V is acceptable. A car battery charger set to low-current trickle-charge works fine.

When charging the battery, check the status lights on your charge controller. There should be a “power on” indicator along with a “battery charging” light.When the batteries are topped off, the “battery full” light will come on.

Do not apply more voltage or current than the charge controller is rated to handle. The controller used in this chapter (shown earlier in Figure 9-13) is rated for 12 V and 21 A. We charged the batteries with a 12 V, 4 A source to match the solar panel output.

Once charged, you can remove the batteries and other components for ease of installation and travel. As you’ve already noticed, Most of the weight in this system comes from the batteries.