In a disaster area or on the battlefield, power is usually provided by diesel or gasoline generators, but delivering fuel to these locations can be costly and dangerous. John Hingley, engineer, founder, and CEO of Renovagen, thought that a renewable power source would be safer and more cost-effective, so he decided to "roll out" a new product: the RollArray, a portable solar array, coupled with a battery bank and a set of inverters. It's a deployable microgrid on a trailer.

The RollArray series comes in two flavors. The MultiGen, pictured above, includes a prewired, roll-out 15 kW solar array, a 53 kWh Lithium Iron Phosphate battery bank, a set of stand-alone PV inverters, and up to three bi-directional battery inverters. MultiGen's big brother, IsoGen, features a 200 kW PV array, an 800 kWh battery bank, and similar inverters. Since they both use the same technology but the IsoGen is a newer design that's slated for a later release, I'll take a closer look at the MultiGen.  

Roll-out Solar Array

MultiGen's deployable microgrid gets its power from a pre-wired roll-out solar array made of copper indium gallium selenide (CIGS) solar cells. Although CIGS devices offer less efficiency than rigid silicon PV panels, they're flexible and much lighter. When rolled up, the CIGS array is 2.2 meters wide and 1.1 meters in diameter. It deploys to a length of 52 meters, making an array that covers about 114 square meters. On a sunny day, that array could produce up to 80 kWh of electricity, depending on its location. On a semi-sunny day, it could generate around 30 to 40 kWh. If there's not enough room for a 52 meter array, it can be partially unrolled with a proportional decrease in power output.

When pulled by a vehicle, the array can be deployed in two minutes, with the entire system setup accomplished by two people in just five minutes. Renovagen estimates that assembling an equivalent array using rigid PV panels would take 22 man-hours. Staked to the ground, the array is designed to withstand winds up to 128 km/h (80 mph).

Batteries

By itself, a fully charged 53 kWh battery bank could deliver 1000 Watts for about two days. Assuming those are semi-sunny days, the 15 kW PV array would easily keep the batteries topped off so they never fall below 50% depth of discharge. With partly sunny conditions, this system could run indefinitely with a reasonable power draw. And because CIGS photovoltaic cells outperform their silicon counterparts under cloudy conditions, it's safe to say that even with several consecutive cloudy days, a MultiGen-based microgrid can produce adequate power continuously.

Lithium Iron Phosphate batteries are similar to Li-ion batteries, but with better thermal stability and somewhat lower cost. In short, they're safer and cheaper than Li-ion batteries. The trade-off is a slightly lower energy density.

Inverters

MultiGen uses SMA Sunny Boy stand-alone inverters, which offer maximum power point tracking (MPPT), 97% efficiency, a wide range of allowable input voltages (125V - 600V), and both single-phase and three-phase voltage outputs. MPPT lets the inverters deliver maximum power under various insolation and load conditions, and the flexible input voltage range assures that the inverter won't shut down under less than ideal sunlight.

The Sunny Boy inverters provide AC power when the array is generating electricity. When the array output exceeds the load requirement, the excess energy goes to the Sunny Island inverters and is used to charge the battery bank. The Sunny Island provides an intelligent charge controller, 96% efficiency, and a multitude of safety features.

The entire MultiGen unit, including shipping container, has a volume of 7.5 cubic meters and weighs around 2000 kg (4400 lbs).

IsoGen

Since there's a little room left on the back of my envelope, I decided to run the numbers on the IsoGen. Its PV array is 250 meters long (almost three football fields) and five meters wide, and can generate up to 200 kW of power. Its daily energy production will vary from 400 kWh (semi-sunny) to a whopping one megawatt-hour on very sunny days. An 800 kWh battery bank can deliver up to 16 kW continuously for two consecutive days with a little left over. Just like the MultiGen, the IsoGen could run indefinitely at reasonable power outputs under partly sunny conditions. The only issue I see with the IsoGen is finding 250 meters of contiguous space on which to roll out the whole array.  

The IsoGen comes in a 20 foot ISO container with dimensions of 6.1m x 2.4m x 2.6m. It weighs 20 tons when fully loaded, including the container itself.

Here is Renovagen's short promotional video:

Renovagen is currently applying for approval from regulatory agencies. The company expects to begin commercial production of the MultiGen around August of 2016. Initial prices vary from £50,000 to £110,000 ($70,000 to $155,000) depending on options, which seems quite expensive until you consider the cost and risk of delivering a steady supply of fuel to a battlefield or a disaster area. By some estimates, that's around $400 per gallon. (Now you can stop complaining about paying $2.50/gallon at the pump.) Nonetheless, Renovagen expects the price to drop significantly as the cost of PV, batteries, and production continues to decrease.

For more information, visit Renovagen's web site or their crowdfunding page.

Images and video courtesy of Renovagen

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