Solar Energy Solar Panel Washington DC Solar
Written by Roger Perry

Practical Considerations for a Battery System

As long as I’ve been doing solar, people have been asking about batteries. The response has always been “yes, we can do them, but it will cost a lot”. That usually ended the conversation.

One question to ask is “why do you want batteries?” Do you lose power frequently? If not, a portable generator will keep your refrigerator, freezer, computers, tv and some lights going. Downsides are; noise, fumes, refueling, having to run extension cords to where needed and putting everything away when power comes back. Not too bad once in a while and it’s very cost effective. Just hope you aren’t out of town when power goes out. There is nothing automatic about this set-up.

If you lose power often and don’t want to do the portable generator dance every few months, you can get a permanently installed generator with automatic start. These are close to $5000 installed for the ones that will run most of your house when the power goes out (a larger one can be installed for a few thousand more that will run everything). This is what hospitals and critical buildings use. Power goes out, the generator starts automatically and powers the house with only a momentary loss of electricity.

Downsides? Noisy, they need maintenance and, if propane or diesel powered, they need the fuel tanks to be kept filled.

What if you lose power often, don’t want the noise, maintenance and fuel expense of a generator? What if you want a system that is environmentally friendly, will turn on automatically, is silent, will run pretty much nonstop without refueling? You should look into installing a battery back-up system connected with a solar system.

What are the downsides? Well, cost is one. While not as expensive as in years past, battery back-up systems are still costly. Compared to a permanently installed generator, battery backups tend to run few thousand more. Ask your accountant but you may be able to take the 30% solar tax credit on the additional cost of the batteries. This brings the price in line with a generator.

Another downside is you can’t run everything in your house. Things a battery cannot run for any length of time are air conditioners or heat pumps, electric water heaters, electric dryer or electric ranges. What they can run are gas or solar water heaters, gas or oil boilers, refrigerators, freezers, lights, tvs, computers, fans and pretty much everything else. Well pumps are on the edge depending on how efficient they are. While running a modern variable speed well pump is not an issue, older well pumps require a large startup current which can be too much for the battery to handle. We are about to install a “soft start” control to try and reduce a well pumps surge demand for one of our customers but the jury is still out.

We are now installing LG Chem lithium Ion batteries. LI batteries have a lot of advantages over the old lead acid batteries. The big advantage they have is they are not damaged by running them dead, whereas lead acid batteries do not like being discharged to less than 50% of charge, a Lithium Ion battery will give you it’s full rating. The one we use is rated for 10 Kilowatthour (KWH). A lead acid battery would need to be rated at 20 KHW to achieve the same capacity. Lithium batteries are also much lighter (not that the customer will have to move them) and can be charged much faster.

The big downsize of LI batteries is the upfront cost compared to LA but they will last much, much longer and they are maintenance free.

In a future blog I will discuss the two different ways to interface a solar system with the batteries, AC coupled and DC coupled and the pros and cons of each as well as what a 10 KWH battery will give you as far as run times for various appliances. I’ll also talk about how a battery system can be retrofitted to your existing solar system.

Solar Service Home Solar Panels
Written by Lisa Walsh

Solar Energy During a Power Outage?

Not quite so cut and dry…

Solar Service ,Home Solar PanelsMost of us who live here in Anne Arundel County appreciate our proximity to the Chesapeake Bay, changing seasons with spectacular Spring and Fall temperatures, and mature wooded areas. However, these pros quickly become cons during snowstorms, thunderstorms and Maryland’s annual hurricane season from late August through October when Hurricanes such as the infamous Isabelle and Sandy blast through our wooded, watery region, bringing floods, downed trees and – the clincher – power outages. If not for the threat of the power outage, we may sit back and enjoy a hurricane as a powerful force of nature, so long as our lights are on, heat or ac is blasting, and refrigerator’s chilling.

Hurricane Sandy caused around 300 thousand power outages here in Maryland, with an estimated 60 thousand in Anne Arundel County alone. It’s a no wonder that many prospective solar system owners – as well as existing solar system owners – want to know if a solar power system can power any of their appliances during a power outage, even if only while the sun shines. Unfortunately, it’s not that simple.

For both functional and safety reasons, there are several additional complexities to a “hybrid” PV system that connects to the grid but also provides backup power during a power outage. To start, during an outage you need to be able to safely isolate your “solar generator” from the grid to protect the line workers. You will also need energy storage (batteries) to balance solar energy supply and household demand. In most cases, you need an additional inverter to convert the batteries’ DC electricity back to AC electricity for your household. Lastly, most battery systems require some level of maintenance as well as replacement one or more times in the lifetime of the solar system. The bottom line is that unless you are willing to pay a nominal 30% premium for a solar system that includes the necessary batteries, transfer switches and additional inverter(s), you might be better served with a more traditional approach to backup power, like a gasoline or natural gas generator, and possibly just for critical loads.

Don’t get me wrong. Hybrid systems are growing in numbers and technology advancements, consumer demand, and smart grid capabilities all will help to drive down costs to make these systems more affordable in the future, ideally making our grid more stable with many distributed sources of energy. In the mean time, most solar installers can offer a hybrid (battery backup) or traditional generator back up options, so you can decide what suits you best.