Solarcraft News

Written by Robert Collins, lead Solarcraft Engineer

The operation of metering, communication, and emergency systems can be maintained by an uninterruptible power system (UPS). Generators fulfill this need in most circumstances, but not without some interruption. When truly uninterrupted power is required, battery-based UPS systems are used to bridge the interruption. These systems can also operate without a back-up generator, entirely from the reserve energy stored in batteries.

There are several types of battery-based UPS systems. Emerging technologies offer promise with increases in efficiency and reductions in equipment cost. However, problems with reliability and utility have slowed industry acceptance. With reliability paramount in back-up applications, focus on tried and true methods for two different applications: the double-conversion AC UPS and the DC UPS.

Written by Robert Collins, lead Solarcraft Engineer

Essential and detailed input calculations and the correct choice of load equipment are vital for the solar-power design of robust remote systems.

Solar electric power is a practical, and in some cases, the only solution for powering remote equipment. Reliable, continuous, autonomous operation of end-use equipment is possible when a robust solar-electric system is in place. Proper system design requires essential inputs: careful choices in end-use equipment, a trustworthy estimation of power requirements, an understanding of the available solar resource and a description of the potential site.

The design of the solar power system naturally follows the selection of end-use, or ‘load’, equipment. However, selecting the right load equipment up front can go a long way in reducing the complexity, size, and cost, of a solar-powered system. Selection of load equipment should be driven by high efficiency and low-power consumption. When a solar system is purchased, essentially a 20-30 year supply of energy is being purchased in one shot. Power wasted is money wasted.

We recently developed a power system for a client that not only distributes power to an entire site, but resolved three specific issues:

• site permits,
• clean compact UPS power generation,
• and consolidation of resources.

This system will be standard equipment for their meter stations across the country.

Problem: Before construction begins at most production sites, permits must be acquired. Site permits require a geotechnical survey and engineering drawings which add time and cost to a project. In areas with lots of oil and gas drilling and production, permitting agencies are busy---and backlogged. It is not unheard of for agencies to take one to three months to issue a permit.

Can specifying a larger charge controller result in faster charging/recharging for lead acid batteries?

Collins: No, and here’s why. A common misconception regarding VRLA (Valve Regulated Lead Acid) is that they recharge quickly. While it is true VRLA can provide substantial discharge currents, on the order of 1 Amp of discharge current for every Amp-hour of capacity, charge currents must be limited to a value much less than this. 

There are two basic reactions that can take place when charging a VRLA battery. One action results in the battery acquiring charge, which is a good thing. The other reaction results in electrolysis, the conversion of water into hydrogen and oxygen, and its not a good thing. The idea is to avoid electrolysis when possible. 

Most VRLA batteries contain a catalyst that combines the hydrogen and oxygen back into water. But this process creates heat and pressure that may result in venting and some loss of water and gas. The loss of electrolyte leads to loss of capacity and eventual battery failure.

June 2012
Solarcraft, Inc.
Sugar Land, Texas, USA

For reliable off-grid electric power at a northern location, redundant power sources are not only prudent; they are key to continuous operation. The trailer that Solarcraft, Inc. built for Hatch combines solar and wind power with a propane generator to keep 1000Ah battery bank fully charged.

The trailer mounted power set is easy to relocate and deploy. Solar and wind power keep the batteries charged, and when solar and wind power isn't enough, the propane generator switches on to recharge the batteries. The smart generator's automatic PLC system monitors load voltage, starts the generator, and shuts the generator off when charging is complete.

A programmable communication device alerts the operator of the status of the power set via text message alerts, so you always know the situation at the site.