The long and short of it is that it wont. Join us today as we discuss how the momentum in the solar industry has already reached a point where it will continue to build. Solar Jobs were 2nd in the energy sector behind oil jobs, and demand is only going up as worn out coal fired plants come offline, utilities respond to the public sentiment, and people take advantage of federal, state,and utility level incentives. I discuss how I think China is competing with us on the R&D side and that we could lose our leadership on this front during the current administration. The reality is that coal jobs aren’t coming back. Storage and Natural Gas technologies will fill the off peak generation gap and as they become cheaper the switch becomes even easier.
Hey everyone sorry for he delay had some unexpected technical difficulties/Still learning how this all works but several finished podcasts will be posted tonight!
Today we will discuss battery maintenance. It is one of the big differences between a grid tied and an off grid system. A grid tied system just sits there and generates electricity either for your home use or to be fed back onto the grid. The battery bank in an off grid system adds a whole new level of complexity. We have previously discussed the types of batteries but for the purpose of this conversation I am going to focus on lead acid batteries. Here are the primary topics for discussion:
- The Chemistry behind discharging and recharging batteries
- Standard Maintenance
- Charging Cycles
- How to measure Specific Gravity and Equalization(overcharging)
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Today we are going to discuss Inverters and the balance of system components. Inverters are the component that takes the DC(Direct Current) Provided by the solar array and stored in the battery bank, and converts it to AC(Alternating Current) for your home use. Alternating current means that the current alternates its direction over and over again(every 8 milliseconds) to create a nice wave pattern. It goes up, rounds off, goes down, rounds off, and repeats.
You want to match your inverter to your battery bank, so if you have a 24V battery bank you don’t want to buy a 12v solar inverter. Once you have cut out or reduced usage of all the devices that you can, you need to do an analysis of the devices you still have and how often they are used to understand what the demands of your inverter are going to be. You need to look at both the peak or startup loads as well as the running loads. For example a refrigerator compressor may draw 5 times its running amps for half a second while starting up. There are many tools on the internet that can help you with this as well, my favorite is over at the Alt-E Store. Once you have your total Watt-Hours per day and your peak loads you can decide on an inverter.
Here are a few things you need to consider while evaluating solar inverter choices.
- Pure Sine Wave vs. Modified Sine Wave – these are the two main classes of solar inverters you will be looking at. Sine waves are that nice up and down curve I spoke about before with rounded peaks and valleys. Pure or True Sine wave Inverters create AC electricity that is just like the grid power. Everything in your house was designed to run on true sine wave. But that doesnt mean that it can run on Modified Sine Wave. MSW is more blocky than TSW. MSW goes up to peak for a few milliseconds, goes to zero for a few milliseconds, and goes down for a fe milliseconds and then repeats. High tech and sensitive electronics may have problems with Modified Sine Wave. Personally, with the price difference not being that much anymore, I would go with the TSW to ensure that I wasnt going to have problems. ANother option would be to have a MSW inverter for normal loads and a seperate smaller TSW inverter for finisky loads.
- Inverter/Charger or not – An inverter/charger is a combination of an inverter, battery charger and transfer switch into one device. When a generator is on an hooked up, or you are hooked to the grid, the inverter recharges the battery bank. It also allows any surplus AC power to pass through and power houseAC loads, such as a television. When AC power is disconnected, the unit inverts DC battery power into AC electricity. I would advise using this because it makes adding a generator to the system plug and play.
- Future expand-ability – Some solar inverters play well with others and can be wired in parallel to expand the system and others cant. If you are building out your system slowly this may be a consideration you should make.
Balance of System – The balance of system is simply the other components you need to complete your system. These include wiring and combining the solar panels, fuses, safety switches, battery cables, disconnects, monitors and controllers or data displays, and mounting systems.
Batteries for Solar Off Grid or Hybrid System
OK everyone, we have covered solar panels, a solar array, and charge controllers, so the logical next step is for us to discuss batteries. Over the lifetime of your system, Batteries will be the most expensive part because the ones that are cost effective when starting a system don’t last very long and the ones that last a relatively long time are prohibitively expensive. Batteries are the center cog of any system because they store the excess energy produces by your source(solar array, generator, or even the grid) and then distribute that energy when generation falls below need.
Here are a few things to remember when considering a battery bank:
- How many days of autonomy do you want? So if your panels stop producing, how long do you want your battery bank to be able to provide energy to the house?
- What climate will the batteries be stored in? Batteries are rated for about 80 degrees, if they are stored at below freezing conditions, you may need 50% more capacity to meet your needs. A cruel fact is that when its cold you normally have less sunlight as well.
- What voltage will your battery bank be? 12v systems are easy but when you start drawing a lot of current it makes sense to step up to 24v or even 48v to reduce the wire size and reduce the number of parallel strings.
- How committed to maintenance will you be? If you want plug and play batteries that you rarely need to visit, expect to pay more than for minimalist flooded lead acid batteries that require regular measurement and maintenance.
We are going to discuss the main categories that batteries fall into and how to use them.
- Flooded Lead Acid Batteries for Solar such as golf cart batteries are the most common off grid battery bank component. They are the lowest cost option, last between 4 and 7 years depending on how well they are cared for and what depth of discharge you normally take them to, and will work pretty well even if you dont religiously equalize and fill them.
- Sealed Batteries for offer some advantages over Flooded Lead Acid because they are relatively maintenance free. They only require a regular full charge. They dont spill or leak fluid, they can be installed in any orientation because you dont need to get to the tops to fill the electrolyte. They are expected to last around 8 years when protected from overcharging.
- Lithium Ion Batteries are the wave of the future, offering 2x the average lifespan of a lead acid battery with higher Depth of Discharge, smaller space and about half as heavy per kWh of storage. The problem with them is that the current charge technology in the market hasn’t caught up with Lithium Ion and they are very picky when it comes to overcharging. Currently I would not recommend Lithium Ion batteries for solar until more research and development is done. The Powerwall may be a solution for grid connected hybrid systems but that’s a specific niche that would require its own article.
- Nickel Iron Batteries are the most expensive but also the most bulletproof batteries for solar systems on the market. They can take 11000 cycles at 80% depth of discharge, with a wide range of operating temperatures and resistance to both over and under-charge conditions. Unfortunately they are very expensive. If you are looking for a battery that will last as long as your solar array, with low maintenance and have the financial means to utilize Nickel Iron this is the battery choice for you.
Well i hope you learned something today, bear with me as I continue to convert the blog to a podcast. I am self teaching as I go and watching a ton of youtube videos and reading a bunch of articles, but implementation will be hit or miss.
Thanks for visiting the blog and check out our other articles if you liked this one or ask questions in the comment section!