Episodes
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Join us today as we discuss Battery Storage vs. Peaking Plants. Peaking plants are power generation facilities that come on only to handle the highest peak loads demanded on the grid. They are meant to quickly ramp up and produce only during the times when the deman is higher than all other generation components can handle. They are very expensive so today we are going to talk about when and how Battery Storage Technology could make them obsolete. At the same time we will talk about the challenges that battery technology will have, even when their cost makes them viable as utility load shifting devices.
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Renewable Energy in Texas is enabling Texas to win the Energy War...OK maybe its not a war but whatever it is they are winning.
Join us today as we discuss Renewable Energy in Texas.
Last year 20% of their energy came from renewables, primarily wind, and on somedays that number was over 40%. Governor Bush signed a bill in 1999 to drive the state towards renewable energy, and then after he became president, Governor Perry increased those goals and helped pass funding bills to improve the infrastructure to make the whole system work. One of the biggest advantages that Texas has is that it has its own grid. -
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Yesterday we spoke about different options for mounting a solar array. Today we are going to dive deeper into ground mount systems and talk specifically about some of the considerations one would need to take when siting a ground mount system in order to get the most optimum solar exposure.
The nice thing about ground-mounted systems is they can be
optimally-aligned with respect to both their southern orientation and their
tilt angle. I use a tool called PVWatts in order to look at the different options for azimuth and what kind of impact that will have over the course of the year. In my area, a more Southwesterly orientation is better than due south when looking at overall system production. Where I live, if I were grid ties, I would have my panels facing about 220 degrees, or 40 degrees off due south.
However since I am more concerned with when I get my energy than squeezing every watt our of daily production, we aren't pointing at 220 degrees. When I get up in the morning I work many times from my upstairs office or my front porch. I need energy in order to run my office machinery to include my routers as well as a fan to keep me cool during the summer, where mornings are pleasant but still hot and muggy. If I were maximizing the daily output, it would be 11 AM before I was getting any real production from my panels. Lets talk for a inut about reducing the amount of shade on the panels. Lets say I have an array of three solar panels. And each of those panels has 72 cells...thats 216 total cells Now if a few of those cells are shaded, they reduce the amount of current that can pass through the system by the proportion of shading on those cells times the total number of cells. So lets say one cell is 50% shaded, now I have the equivalent of 1.5 panels worth of energy coming from my three panels. In other words by shading one out of 216 cells, I have erased the generation of 108 of those cells. That's not a good utilization of my investment at all. The reason for this is that every cell in the string has to operate at the current set by the shaded cell.
One strategy for mitigating this issue is to place panels that may recieve shading on a parallel string, so that only the string the shaded cells are in is affected and all the parallel strings are not. This is how our system is set up in that the eastern most string which receives early shade, and the westernmost string which receives evening shade, wont impact the other two respective strings.
An interesting emergiung tech is Module Level Power Electronics which are essentially microinverters that operate on the individual module level and therefore limit shading losses to a single panel. These are initially more expensive but in the right environments can pay for themselves over time. I plan to do a stand alone show on microinverters in the future. Some panel manufacturers are also looking into in panel electronics that may act as microinverter for each cell, limiting the shading losses to the individual cells that are shaded and not impacting any of the other cells on that panel.
As with any solar project, ground-mounted PV systems must be designed with care to meet your individual goals and address practical issues. Siting issues for ground-mounted systems are different than for roof-mounted systems and include such things as property boundaries, terrain, soil properties, the location of electrical interconnections and potential permitting issues. But in addition to these general siting concerns, energy generation optimization in a ground-mounted system (or, for that matter, on most flat-roof installations) must address the unique issue of how to space the rows of solar panels to maximize energy harvest while preventing the panels from shading one another. This issue can of course be avoided by simply keeping the rows of panels sufficiently far apart, but generally one needs to minimize this inter-row spacing to most efficiently utilize the available site. -
Mounting Options for Solar Arrays:
Ok folks, there are two options for mounting solar panels. One is roof mount, the other is ground mount. We are going to discuss the pros and cons of each and Ill sprinkle my opinion in along the way.
Rooftop solar arrays are restricted by the characteristics of the roof on which they are installed. If your roof is at a bad angle, doesn’t face south, or has obstructions like chimneys or skylights, then your solar array will be less productive. On the other hand, ground-mounted solar panels can be located wherever the conditions are best.
Generally, ground mount solar panels cost a bit more than rooftop solar on a per-watt basis because of additional labor and permitting that may be required for the installation. That being said, if your property isn’t ideal for rooftop solar, installing a ground-mounted system can actually save you more money in the long run.
In addition, if your home uses a lot of electricity, your roof might not be big enough for a solar energy system that meets your electricity needs. In contrast, ground-mounted solar systems can be sized to match your electricity consumption without the space restrictions of a rooftop system.
One of the reasons we tell people to perform an energy audit, and put together a usage reduction plan first, is that if you dont, you are going to run out of real estate(roof or ground) before you meet your needs. If you need 1200 sq ft of roof dedicated to solar, but only 800 sq ft of your roof faces south, you can see what I mean. Now that being said if you are going to be going with a roof mounted system, and you have already maxed out your conservation, then going with more efficient, but also more cost per watt panels may be the right option for you.
When you mount on your roof, your panels are going to be hader to access to maintain, and we know clean panels are always the goal. Not cleaning pollen, dust, and other buildup from panels can have a big impact on your output. Snow buildup is another consideration that must be taken into account for a roof system. you cant easily get onto the roof to clear snow after a storm when your panels are on the roof. Additionally, in the summer your panels will be hotter because there is less airflow behind them up on your roof. Hotter panels are less effective.
When mounting solar panels on your roof, you take advantage of a space that is otherwise not being used. You are not sacrificing precious rreal estate on the ground, and while im not aware of any studies, I would imagine that the little bit of shade on the roof itself may have a degree or two impact on your attic temps which might reduce your overall cooling load in the summer. You dont have to dig a trench to bury transmission lines with a roof mount, and there is no excavation or heavy equipment needed for a roof mount system.
Now lets talk a bit more about ground mount systems. Obviously when putting in a ground mount system, you can place the panels at the exact tilt and azimuth you choose, which is best for your goals. Due south might not be the best option in your are due to shading considerations.
The ideal is to have a shade-free array throughout the entire day, from dawn until dusk. However, obstructions such as trees, buildings, and mountains are common. Early morning and late afternoon sunlight isn’t as powerful as those midday hours, so aiming for a shade-free “solar” window from 9 a.m. to 3 p.m. will give you most of the energy available at the site assuming that you dont have any shading issues. If you have great sun from 10 to 5, like we do at our homestead, you might cange your azimuth a little bit to take advantage of that. Ground mount also allo for multiple azimuths, so you might have most of your panels facing one direction, but have a few panels off by a few dozen degrees to take advantage of afternoon or morning sun, as your conditions may require.
Now when working on a ground mount system, -
Today we will discuss the most efficient active methods for utilizing solar energy: Solar Thermal. We will discuss air and water heating and different options.
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Today we're going to talk about the grid of the future. I was at. Actually over the past year I've been at several power generation conferences where I've had conversations with people from companies like Duke Energy Southern Company which owns Alabama and Georgia Power Mississippi Power and Gulf Power. And let's see who else...Ameren over in the Midwest. I don't deal with the ones out west very much. Dynegy and Luminant over in Texas all of these guys are saying the same thing the grid of the future is coming and it's going to look a lot different than what we have right now. And it's going to surprise a lot of people how different that it is. And so when I was out this last one down in Alabama.
I was talking to a guy and he was telling me that both Alabama Power and Georgia Power are creating smart neighborhoods. So these companies that make their money off of converting nuclear reactions and coal dug from the ground to energy or to heat which then creates steam which creates energy. These guys are investing quite heavily in renewables and now in what they're calling the grid of the future and so. I thought to be interesting to talk through some of that stuff today. If you go to a smart neighbor dot com that's the Web site for this program that they're doing and it's really neat. I mean it's super high efficiency appliances smart houses you know where things are voice activated and your refrigerator tells you when you're running low on milk and you can change your thermostat from your cell phone while you're at work. All of these things and then it's also there all the houses have solar panels on them.
The neighborhood itself has a natural gas powered backup generator. And then there's a micro grid for the neighborhood. And what's needed about that micro grid is it allows properties that are generating an excess of electricity from their solar panels to take that and put it onto the micro grids so that another person in their neighborhood can utilize that without having to pull any electricity off of the bigger overall grid. And so this essentially creates a fully self-sufficient neighborhood. We talk about self-sufficiency a lot and how you know solar thermal solar photovoltaic systems can be part of that self-sufficiency. But this is a system that that extends out from just the house itself and goes to the neighborhood. And I think about what that might do for a community.
One of the things that happened when we know they are able to take these vast amounts of energy from certain places in the country transport them on railroads to other places in the country generate electricity and then through the magic of alternating current. Transfer that electricity all over the United States and create these massive grids with this step down transformers and all these different things one of the things that that did was it created the ability for humans to exist without community. It created the ability for people to you know either move far away from other people and still have access to all the things that they really wanted. Or you know to move out of the city and away from the customs around there being everyone in a neighborhood knowing each other and talking to each other and helping each other out and getting together for cookouts and things like that you know that. Those are pretty strong customs in the in the cities and where people started moving out to the suburbs a little below that stuck around. But you know by the way the 70s and the 80s you weren't talking to your neighbor in the suburb that much. And by the 2000s you might not even know your neighbor's name.
And so what I'm hoping is I look at some of these technologies and one of the things that I think about is well if you're buying electricity from me Monday and Tuesday and I'm buying it back from you Wednesday through Thursday and then Friday Saturday and Sunday when we're home you know we're sharing the grid we all go maybe four of us guys get togethe... -
Thanks for joining us today as we give a brief rundown of where the homestead is here in the Summer and what our plans going into the Fall will be. We have focused on "Zone 1" for all you permies out there and are very pleased with the results of the new Aquaponics system. That being said our rainfall through this hottest portion of the year has been pretty abysmal so Operation green front yard has not gone as well as planned. I am pleased to say that our need to run the AC units has been very low this year, reducing the amount of time we may have otherwise needed to run the Generator. All that being said our batteries are nearing the end of their life cycle after 6 years hard time on the homestead. As always, shoot us an email at [email protected] with any questions you may have. Anyone interested in consulting work please visit our
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Today we're going to finish up the conversation we started yesterday about taking a Holistic View of Energy Use in the Household and reduction of that use where possible. We really hit on the big topics yesterday. And so I'm not going to do any deeper dive into those. Those are the areas where you're using the most of your energy right now. And so therefore they provide the easiest opportunity to put plans in place to reduce that use. But some of the things they're going to talk about today as we finish up the conversation is going to be water usage insulation and windows.
So when we talk about water really the number one thing that we're talking about is how to reuse greywater. The fact that we take potable water and put it into a toilet so that we can flush waste into a septic system is almost a crime when you consider so many places in the world that don't have access to potable water. A simple system like installing a sink on the back of your toilet. So when you wash your hands after using the bathroom that water from washing your hands goes down into the tank and then that water becomes the water that gets used on the next flush. That's a really inexpensive easy install system that helps with this problem.
Another one would be a system that recycles the water from your bathtub and uses that for flushing water so for showers and baths and that it gets a little bit of treatment enough to make it not go bad. It is gray water it's not portable. And then using that for flushing water is a really nice system. The thing that you could do is in addition to try to come up with an idea for utilizing that gray water for flushing your toilet. What we do utilize a portion of it or all of it for outside irrigation for gardens and lawns and things like that you know installing systems that are going to do a pre filter or inheres the reality a little bit of bleach. I mean a little bit of Bleach goes a long way to make sure that you don't have a stagnant stinky you know water storage in between using a shower and using that shower water on your front yard. It's a great way to reuse it realistically if a household were to get really serious.
They could reduce their water usage by 50 percent 30 percent is a pretty conservative estimate and I've seen estimates as high as 80 percent now. Not really sure how many times you'd have to reuse water to reduce your overall use by 80 percent. But those are the systems that give that kind of water reduction are pretty involved. They're probably not very energy efficient or energy neutral and realistically those are for areas that don't get enough rainfall don't get enough or don't have access to very good municipal water systems. But a 50 percent reduction is doable. And like I said a 30 percent reduction is easy with some very simple systems.
I really believe in reduced flush and restricted flow showerheads. I know a lot of people that want their shoulder to split their hair you know or part their hair when they're taken. I don't necessarily need a shower that's that powerful. Our shower at the office off grid homestead is I believe a gallon and a half per minute which is still I mean there's a lot of you out there you can get four a gallon and Minahasa a gallon and a half. You know and you know 70 ish. My wife who has very thick hair doesn't have a problem doing what she needs to do to get her hair washed and all that. So with me I have relatively thin air a bucket of water would do me just fine. But you know using those reduced flush I think we got to one point three leader per flush system that handles anything we throw at it that restrict it flow showerhead you know is a big deal you could put restrict flow faucets on your sinks and it's just a simple situation of the vast majority of the water that comes out comes out hits the fixture and goes down the drain without ever touching us. So if we could get a system in place where we're just reducing the amount per minute of water t... -
Today we're going to talk about a holistic view of energy use in the household.
This is not going to be specifically about solar energy any of the things that I'm going to talk about today are things that it could definitely be be used on a household that is on the grid off the grid on the grid with grid solar or it doesn't really matter. It's not a solar specific podcast it's about evaluating your energy usage identifying ways to potentially reduce that usage and conserve your cash. Because in most situations the more energy you use the more cash outflow you have to pay for it. And that energy may be in the form of firewood and maybe in the form of a propane or natural gas or might be electricity. So you're some of the things that we're going to talk about in no specific order. We're going to talk about heating and cooling and talk about Limiting water usage. Talk a little bit about appliances consumer appliances things like that. Want to talk a little bit about insulation windows things that you can do to keep your money inside after you've spent it. And anything else that may pop up as we go along. So. The first thing and this makes a whole lot of sense because it is the place where most of the energy usage in any household exists is conditioning the space whether that be cooling or heating it. And in some areas the humidified that's going to be your biggest annual spend and that's pretty common for just about everyone in the U.S.
If you live in the South you may not be as much in the winter but you're cooling a lot more during the summer and vice versa if you're in North now as someone that lives off grid. I can tell you that I would much prefer to live in a cooler climate because it's much easier for me to go out and pick up and cut up deadwood from my own property and burn that in the winter or even pay someone if someone's got cheap firewood in my area pay someone for firewood and then burn that for heat in the house. That's much easier for me to do. What's more cost effective for me. Than it is to try to keep my house cool in the heat of the summer. We do a pretty good job. We have some systems in place that allow us to cool and stay cool and stay comfortable at night without spending a lot of money that we don't want to spend. But in terms of overall usage it's actually typically cheaper in the south because electricity is cheaper compared to some of the other things like propane and heating fuel diesel and things like that. Some of the other things that people that don't heat with wood with up in the north their winter bills are way more expensive than the highest.
Several bills in the south unless you've just got some crazy bad insulation or inefficient system going on. So one of the options that someone could use and we'll start with cooling would be to take a look at basically three different strategies. One is evaluate the system that you're using for cooling. There's something called a seasonal energy effectiveness rating or sear. That. Rating. Really is I mean one number change is going to have a pretty decent impact on what you're going to spend to cool air space over the course of a year or over the course of several years or even decades. So take a look at what you've got in place and making sure if you're in a position where you can change or in a position where you have to change your system without getting those higher efficiency ratings may cost more upfront with that money is absolutely going to pay for itself over time many times over the next thing is and I'm sure you've heard it before but I would be remiss if I didn't mention it but set your thermostat to reasonable levels if you live in Texas and you're getting 110 degree days you shouldn't have to have your system set up 68 degrees to feel comfortable in the house. Honestly where we live we don't even get that high and we're typically if we can keep the house in the high 70s to even up to maybe 82 83 we're comfortable especially if y... -
Join us on the podcast today as we discuss evaluating when off grid solar makes sense. Utilizing an off grid strategy can make sense once you have made the decision that is what you want to do. But the reality is that taking an on grid property off the grid compared to buying an off grid property or building one from scratch are very different financial decisions. We discuss taking a holistic view of going off the grid but keep the focus mainly on the financial side, with a small tangent discussing internet connections in places where there are no power poles. Off grid solar can make sense from a financial perspective particularly when evaluating the cost of home and land acquisition compared to grid tied properties.
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January 2018
As we sit here in the dead of winter dreaming of spring but also enjoying the reduced pace of the winter on the homestead, I thought it would be a good time to give an update as to where we are with our projects around the homestead as we build towards a more self sufficient lifestyle. One of the nice things about winter for me is that I can more easily control the climate within the house. Obviously during the summers with a house that doesn’t have central AC and is limited to the energy that can be produced by the sun, and with the understanding that solar thermal is much more efficient than solar photovoltaics, it can be a struggle to keep the house comfortable during the day. Cooling the rooms we are in only, combined with strategic shading and plenty of personal level fans for moving, ends up being a good strategy. However in the winter, where we heat almost exclusively with wood, utilize proper clothing and nice comfy thick blankets on the beds, it is much easier to dial in exactly the climate we want.
The kitchen remodel has progressed to the point where the kitchen is completely functional again, albeit not completely finished. It turns out going from standing tree to kitchen counters and cabinets isn’t as easy as it doesn’t sound! Now that it is really too cold to work full time outside in the cold, I’ve decided to table this project until next Fall.
Another nice thing about the winter is that we are no longer using irrigation water, so we are definitely catching more rain than we are using, and this will likely stay that way until the dead of summer.
The combination of no cooling, less water pump use, and less power tool use leads to a nice capability of only having to run the generator when we are equalizing the batteries, which can be once a month. Even in the winter where we get less battery capacity, we rarely if ever need to run the generator to add capacity. Clothes washing and dish washing is still done in the middle of the day when the sun is full on the solar panels, but we do end up taking things to the laundomat in town to dry sometimes.
We did lose our chickens over Christmas while we were out of town, not sure what but something got into the chicken pen and wiped them out. I’m thinking about putting another enclosed area up near the house and perhaps moving them up there in the winter because we have no need to walk down to the garden in winter other than the chickens and bringing them closer to the house will bring them closer to human and dog smell, as wlel as providing an opportunity for us to beef up that enclosure to help protect them.
We did decide to liquidate our quail flock, which ended up in a great graduation ceremony for the birds and very nice BBQ to follow. We did find these birds were a bit more tough than the ones we had graduated right around 7 or 8 weeks. That being said the flavor was very good, but I may alter the preparation method the next time we process mature birds. Im thinking a long and low smoke with a nice purpose made rub.
We’re starting plans to erect a 10’ uncovered extension to our existing back deck, and enclose the covered portion of the deck, specifically to provide a nice place to be outside in the winter but out of the elements.
We did lose our hot water heater, and I’m hoping it is an easily fixable electrical issue, as the fuses were blown when I took the cover off, but if not we will need to replace the hot water heater, yay! That will be a project for next week, but luckily we do have a backup water heater in the bathroom that allows us to take showers with a 20 lb propane tank, but we can also wash dishes in the tub, and put the dish drainer in there as well. Its not ideal for either weater efficiency or back pain, but it works.
We also have some extra dish strainers and some plastic tables so setting up an outdoor dish station to run through a big batch of dishes is also doable on days where we have good sun and its not t... -
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.
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Battery Maintenance
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)
After listening to the podcast if you have questions please email them to me at [email protected] or add them to the comment section of the blog. Additionally you can go to our Facebook page to get more information or to ask questions.
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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! -
Charge Controllers, what are they?
OK so we have covered what solar panels are, and how to design a solar array, but what happens once your panels are generating power? Well you obviously want to get them into your battery bank, but other than some very specific situations, you will charge your batteries through a charge controller. So what is a charge controller...in essence, it is the device that regulates the amount of energy, both in terms of voltage and amperage, that goes from your solar array to your battery bank.
Charge controllers come in two primary modes, Pulse width modulation(PWM) and Maximum Power Point Tracking(MPPT). Pulse Width Modulation Solar Charge Controllers reduce the amount of voltage applied to the batteries in an inverse relationship to the charge level of the batteries. So as the state of charge goes up, the voltage is reduced so as not to damage the batteries. MPPT Solar Charge Controllers match the incoming power from the PV array to the most efficient use of that power in terms of charging the battery. This allows the array and the battery bank to be vastly different voltages. The ability to step up the voltage and therefore reduce amps(because watts always equals amps x volts), especially if the array is sited a long distance from the charge controller, can allow a person to pay for the charge controller in wire savings. This is because higher voltage/low amp power can run through thinner wires from the PV array to the Charge Controller. To give you an example, using 6 gauge wire vs. using 2/0 gauge wire can save you nearly 70% in wiring costs.
We will dig into MPPT chargers in more depth at a later date. Feel free to ask questions in the comment section below. -
Sizing a Solar Array
A Solar Array is just a fancy term for your solar panels, which themselves are combinations of solar cells, combined into a single system. Today we discuss "sizing a solar array." The first step is determining what your needs are. It is always good to eliminate or reduce some parts of your usage before determining the size of your solar array. For example at our house we got rid of our drip coffee maker and began buying roasted beans, hand grinding them, heating water on a propane stove, and using a french press. The amount of electricity we need to make our morning coffee is now zero. Switching to LED lighting, putting appliances on surge protectors that we turn off when not using, and drying our clothes on the line rather than in an electric dryer were some other adjustments we made before going off grid.
If you are currently on grid, you have a very easy meter to determine your usage in your monthly electric bill. Depending on your climate, you may see higher usage during certain times of the year. For example in TN, we saw summer months where we were cooling with electricity as our major power need. One hard rule we have living off grid is that we don't use electricity to generate heat. No electric furnaces, space heaters, microwaves, hot plates, crock pots, or electric water heaters for us. So my suggestion would be to reduce your consumption as much as possible, then review your bill to see how much electricity you are using. In the US, the average utility customer uses 901 kWh per month of electricity. Your bill will be denoted in kWh which means kilowatt-hour, Or 1000 watts for 60 minutes. For the sake of this example, lets assume that you have dropped your consumption to 450 kWh per month(half the average household). So on average you are using 15 kWh per day. Once we have this information we need to look at an insolation map, which will show you the average daily hours of sun you receive in your location. Here is a map of the us provided by the NREL.
Armed with the insolation data you have for your location, back to sizing a solar array. You need to divide your daily use by the number of hours you get. The NREL posts maps for each month so you could break this down month by month and use the worst case scenario if you like. Where I live in TN we average 4.5 sun hours per day. This means over the course of an average day, we get the equivalent of 4.5 hours of full sun. So using our above number of 15 kWh per day and 4.5 average hours of sun, the total array size that I need is 3333.33 watts. You will notice I went ahead and made the conversion from kWh to watts. Now you can figure how many panels you need in your array to meet your needs. You may decide you want to replace 50% of your needs, or you may go all out and decide to take out all 3333 1/3 watts. Lets take the latter and assume we are going to get a great deal on 10 or more 310 watt panels. We divide the wattage of the panels into the watts needed, so 3333.33/310, which gives us 10.75 panels. My suggestion is to increase this number by 25% to account for losses at different points in the system(which we will discuss later). Doing this gives us 13.44 Panels, which we will round up to 14. If you followed along, you now now exactly what your usage is, how much you want to replace with solar, and how many panels you need at a specified wattage to meet your needs. We hope this post on "Sizing a Solar Array" was helpful. Shot us an email on our Contact Page if you have any questions we would be happy to help! -
How do Solar Panels work?
Solar, or Photovoltaic, Panels work by converting light energy from the sun, or photons, into electricity through the "Photovotaic effect." Interestingly, a French physicist built the first ever photovoltaic cell at 19 years old, in 1839. The first practical photovoltaic cell was demonstrated by Bell Laboratories in 1954 and early on they were primarily used in space.
A Solar Panel is a collection of solar cells that are made up of semiconductors. Semiconductors absorb the photons--through a process I wont describe in detail--and cause electrons to be excited and break free to be converted into usable DC electricity. Solar cells are arrangements of silicon "sandwiches" where one layer is activated with boron and the other activated with phosphorus. This helps the charge to be created and directs the free electrons to the wiring that leads to your charge controller.
The key to remember here is that its the light energy that is converted to usable electricity, so when siting a group of solar panels, also known as an array, you should do an insolation analysis, which is a fancy phrase for looking at whether or not you are going to have full sun hitting the panels or if there will be shadows cast from structures or vegetation. A part of this analysis will also be determining how much full sun you get in your area and using that information to determine how many panels you need to charge your battery bank.
This post is about "how do solar panels work" but now that you have a basic understanding, here are a few things to remember that can reduce to the amount of energy your panels can produce: dust/pollen/leaves, temperature, and wire resistance. If you let your panels get dirty or accumulate leaves or snow, it should be quite obvious that the light cannot reach the covered up cells, which will logically result in less energy production. When your panels heat up, they also become less efficient. Remember above when I discussed the electron becoming excited and breaking free? Well the hotter the cell gets, the less potential there is between the different electrons because the ones that are at rest are already a little "excited" because they are hot. As a matter of fact when sunlight shines in through your window and heats the air in your house, this is specifically due to excited particles, and its no different with a solar panel. We will discuss wire sizing in more detail in another post, but remember that current is measured in amps, and wire resistance simply means that smaller wires cannot handle high amps. This is why we use ideas such as stepping up voltage the reduce the number of amps required to move the same amount of energy. Amps x Volts always equals Watts so increasing one number always decreases the other.
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Types of solar installations
There are a variety of ways to harness the power of the sun. Today we are going to define the ways and discuss them:
Grid Tied
Off Grid
Hybrid
PV Direct
Solar Thermal
Photosynthesis
Grid tied
Grid tied systems are solar installations that are implemented on a property that uses utility energy from the grid. These systems reduce the amount of energy purchased from the utility company and the amount of energy not purchased is used to offset the cost of the installation. These systems must have safety switches that cut the connection off when the grid goes down so that you are not feeding solar energy onto the grid while linesmen are trying to make repairs.
Off Grid
Off Grid systems are solar installations that generate and store electricity in batteries for use when the power needed is greater than the power being produced, such as at night or on cloudy days. These systems are not tied to the grid and do not have safety cutoffs. Many people install off grid systems to provide power only during power outages, and only to power certain appliance such as refrigerators to avoid spoilage. Others have full off grid systems on hunting cabins or remote properties where there is no access to utility power. Many times off grid systems will include a Generator to keep batteries charged up during period of prolonged low generation or high usage.
hybrid
Hybrid systems are grid tied systems with battery backup. They add a layer of complexity because not only do you need to keep your system disconnected from the grid when utility goes down, but you need to switch over to battery power, and for most people drastically reduce your energy consumption. The typical battery bank cannot support the typical household usage for very long. These systems sometimes add yet another layer with a whole house generator.
PV DIRECT
PV Direct is the most simple way to implement a solar electric system. This system utilizes a PV panel wired directly to a load such as a solar powered water pump. This is a great way to utilize water as a battery, as in pumping water to a higher elevation and then letting gravity distribute it. Another option would be to use a solar panel wired to a fan that circulates hot air out of your attic to assist with colling your home, or even blowing air on yourself.
SOLAR THERMAL
Solar thermal is probably the second most efficient way to utilize the power of the sun and it is quite simply to use the radiant heat from the sun to reduce energy needs for heating. This could be heating water using a solar water heater, heating air, or heating a thermal mass such as when passive solar is used to heat a house or greenhouse by storing heat and releasing it over time when the temp drops.
PHOTOSYNTHESIS
Photosynthesis is the most efficient way to utilize the power of the sun as we combine that power with nutrients in the air and soil to allow plants to produce food, shade, and building materials for us. We would be remiss to create a solar site without acknowledging the power of photosynthesis and developing ways to leverage it to our own benefit.
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Energy vs. power
This short series is to help build some foundational knowledge that will help you understand the building blocks of Solar.
energy
Energy is the capacity to do work. Measurements for energy include calories, BTUs, Joules, and Watt-Hours. We would use the term energy when discussing how much capacity you have in your battery bank. If you are on grid you will get a utility bill from the power company and that will normally provide you with the number of kWh or Kilowatt-Hours you used last month. A Kilowatt is 100 watts and a watt hour is one watt being used for one hour.
POwer
Power is the rate of consuming or producing energy. Watt is the unit of measure we use do discuss power. A watt is defined as amps multiplied by volts. A solar panel rated for 100 watts can produce 100 watts ofpower at any given time under perfect conditions. If it produced those 100 watts for 1 hour it would store 100 watt hours of energy. Understanding that a watt is always equal to one volt multiplied by one amp will be very important as we continue this series.
Two considerations when sizing solar systems are how many watt-hours of storage do you have(ENERGY) and how much power can the system deliver at any moment(POWER)
