What are the benefits of grid-connected solar panels vs. living off the grid? Deciding whether or not to grid-tie your solar panels is usually pretty straightforward – the clear-cut benefits of being grid-tied appeals to the majority of homeowners. There are, however, some people that choose to live off the grid.
What would be the best in your situation? Let`s look closer at the benefits and downsides of grid-tied, off-grid and hybrid solar systems.
Grid-Tied Solar Systems
Grid-tied, on-grid, utility-interactive, grid intertie and grid backfeeding are all terms used to describe the same concept – a solar system that is connected to the utility power grid.
Advantages of Grid-Tied Systems
1. Save more money with net metering
A grid-connection will allow you to save more money with solar panels through better efficiency rates, net metering, plus lower equipment and installation costs:
Batteries, and other stand-alone equipment, are required for a fully functional off-grid solar system and add to costs as well as maintenance. Grid-tied solar systems are therefore generally cheaper and simpler to install.
Your solar panels will often generate more electricity than what you are capable of consuming. With net metering, homeowners can put this excess electricity onto the utility grid instead of storing it themselves with batteries.
Net metering (or feed-in tariff schemes in some countries) play an important role in how solar power is incentivized. Without it, residential solar systems would be much less feasible from a financial point of view.
Many utility companies are committed to buying electricity from homeowners at the same rate as they sell it themselves.
2. The utility grid is a virtual battery
Electricity has to be spent in real time. However, it can be temporarily stored as other forms of energy (e.g. chemical energy in batteries). Energy storage typically comes with significant losses.
The electric power grid is in many ways also a battery, without the need for maintenance or replacements, and with much better efficiency rates. In other words, more electricity (and more money) goes to waste with conventional battery systems.
Additional perks of being grid-tied include access to backup power from the utility grid (in case your solar system stop generating electricity for one reason or another). At the same time you help to mitigate the utility company`s peak load. As a result, the efficiency of our electrical system as a whole goes up.
Equipment for Grid-Tied Solar Systems
There are a few key differences between the equipment needed for grid-tied, off-grid and hybrid solar systems. Standard grid-tied solar systems rely on the following components:
- Grid-Tie Inverter (GTI) or Micro-Inverters
- Power Meter
Grid-Tie Inverter (GTI)
What is the job of a solar inverter? They regulate the voltage and current received from your solar panels. Direct current (DC) from your solar panels is converted into alternating current (AC), which is the type of current that is utilized by the majority of electrical appliances.
In addition to this, grid-tie inverters, also known as grid-interactive or synchronous inverters, synchronize the phase and frequency of the current to fit the utility grid (nominally 60Hz). The output voltage is also adjusted slightly higher than the grid voltage in order for excess electricity to flow outwards to the grid.
Micro-Inverters
Micro-inverters go on the back of each solar panel, as opposed to one central inverter that typically takes on the entire solar array.
There has recently been a lot of debate on whether micro-inverters are better than central (string) inverters.
Micro-inverters are certainly more expensive, but in many cases yield higher efficiency rates. Homeowners who are suspect to shading issues should definitely look into if micro-inverters are better in their situation.
Power Meter
Most homeowners will need to replace their current power meter with one that is compatible with net metering. This device, often called a net meter or a two-way meter, is capable of measuring power going in both directions, from the grid to your house and vice versa.
You should consult with your local utility company and see what net metering options you have. In some places, the utility company issues a power meter for free and pay full price for the electricity you generate; however, this is not always the case.
Off-Grid Solar Systems
An off-grid solar system (off-the-grid, standalone) is the obvious alternative to one that is grid-tied. For homeowners that have access to the grid, off-grid solar systems are usually out of question. Here`s why:
To ensure access to electricity at all times, off-grid solar systems require battery storage and a backup generator (if you live off-the-grid). On top of this, a battery bank typically needs to be replaced after 10 years. Batteries are complicated, expensive and decrease overall system efficiency.
Advantages of Off-Grid Solar Systems
1. No access to the utility grid
Off-grid solar systems can be cheaper than extending power lines in certain remote areas.
Consider off-gird if you’re more than 100 yards from the grid. The costs of overhead transmission lines range from $150,000 per mile (for rural construction) to $5,000,000 per mile (for urban construction).[2]
2. Become energy self-sufficient
Living off the grid and being self-sufficient feels good. For some people, this feeling feeling is worth more than saving money. Energy self-sufficiency is also a form of security. Power failures on the utility grid do not affect off-grid solar systems.
On the flip side, batteries can only store a certain amount of energy, and during cloudy times, being connected to the grid is actually where the security is. You should install a backup generator to be prepared for these kinds of situations.
Equipment for Off-Grid Solar Systems
Typical off-grid solar systems require the following extra components:
- Solar Charge Controller
- Battery Bank
- DC Disconnect (additional)
- Off-Grid Inverter
- Backup Generator (optional)
Solar Charge Controller
Solar charge controllers are also known as charge regulators or just battery regulators. The last term is probably the best to describe what this device actually does: Solar battery chargers limit the rate of current being delivered to the battery bank and protect the batteries from overcharging.
Good charge controllers are crucial for keeping the batteries healthy, which ensures the lifetime of a battery bank is maximized. If you have a battery-based inverter, chances are that the charge controller is integrated.
Battery Bank
Without a battery bank (or a generator) it’ll be lights out by sunset. A battery bank is essentially a group of batteries wired together.
DC Disconnect Switch
AC and DC safety disconnects are required for all solar systems. For off-grid solar systems, one additional DC disconnect is installed between the battery bank and the off-grid inverter. It is used to switch off the current flowing between these components. This is important for maintenance, troubleshooting and protection against electrical fires.
Off-Grid Inverter
There`s no need for an inverter if you`re only setting up solar panels for your boat, your RV, or something else that runs on DC current. You will need an inverter to convert DC to AC for all other electrical appliances.
Off-grid inverters do not have to match phase with the utility sine wave as opposed to grid-tie inverters. Electrical current flows from the solar panels through the solar charge controller and the bank battery bank before it is finally converted into AC by the off-grid-inverter.
Backup Generator
It takes a lot of money and big batteries to prepare for several consecutive days without the sun shining (or access to the grid). This is where backup generators come in.
In most cases, installing a backup generator that runs on diesel is a better choice than investing in an oversized battery bank that seldom gets to operate at it`s full potential. Generators can run on propane, petroleum, gasoline and many other fuel types.
Backup generators typically output AC, which can be sent through the inverter for direct use, or it can be converted into DC for battery storage.
Hybrid Solar Systems
Hybrid solar systems combines the best from grid-tied and off-grid solar systems. These systems can either be described as off-grid solar with utility backup power, or grid-tied solar with extra battery storage.
Advantages of Hybrid Solar Systems
1. Less expensive than off-gird solar systems
Hybrid solar systems are less expensive than off-grid solar systems. You don`t really need a backup generator, and the capacity of your battery bank can be downsized. Off-peak electricity from the utility company is cheaper than diesel.
2. Smart solar holds a lot of promise
The introduction of hybrid solar systems has opened up for many interesting innovations. New inverters let homeowners take advantage of changes in the utility electricity rates throughout the day.
Solar panels happen to output the most electrical power at noon – not long before the price of electricity peaks. Your home and electrical vehicle can be programmed to consume power during off-peak hours (or from your solar panels).
Consequently, you can temporarily store whatever excess electricity your solar panels in batteries, and put it on the utility grid when you are paid the most for every kWh.
Smart solar holds a lot of promise. The concept will become increasingly important as we transition towards the smart grid in the coming years.
Equipment for Hybrid Solar Systems
Typical hybrid solar systems are based on the following additional components:
- Charge Controller
- Battery Bank
- DC Disconnect (additional)
- Battery-Based Grid-Tie Inverter
- Power Meter
Battery-Based Grid-Tie Inverter
Hybrid solar systems utilize batter-based grid-tie inverters. These devices combine can draw electrical power to and from battery banks, as well as synchronize with the utility grid.
The bottom line is this: Right now, for the vast majority of homeowners, tapping the utility grid for electricity and energy storage is significantly cheaper and more practical than using battery banks and/or backup generators.
Author: Mathias Aarre Mæhlum
Hi Mathias, I like your website.
I have an idea that I am struggling to find any resources to back it. First of all I graduated last year with master in renewable energy from Warsaw university of technology. I work currently in the UK, but very soon will be returning to Poland as my employer is going under. Before I tell you about my idea, we can agree that there are 3 main types of domestic solar systems;
1- grid tied
2- stand alone system
3- Hybrid which is actually grid tied with battery back
You mentioned these three types in your article. Now in order to have grid tied or hybrid system you need to know that your utility company will buy the excess energy otherwise you will b dumbing this energy for free in the grid right?
then what is the solution for a country that yet to adopt any feed in tariff system (like Poland)?. the only solution then is stand alone. but we know that such systems are extremely expensive if they are to supply a normal size house throughout the year. The reason is that we have to build a very large system to provide enough power during winter.
Now my idea is to build a system that stands alone, but have the flexibility to switch over to utility power when we run out of juice. The system that I am thinking of should be sized to provide all the energy that a house needs during the best irradiation day in the year. the system like any stand alone system consists of panels batteries, inverter, and a new component is Automatic Transfer Switch, which is going to to switch over to grid power once the inverter shuts down. I ran few simulation for such a system and find that it works fine. The advantage of this system is:
1- you need minimal amount of PV panels
2- you don’t need large battery bank as in stand alone systems
3- most importantly its very reliable compared to stand alone
sizing the system to highest irradiation day in the year means that, the system can’t provide all the energy needs for mare than few days, the simulation results showed that such a system provide about 50% of the annual electricity needs of a house in the Polish climate.
I can’t find any resources that could support my idea, therefore I am afraid that I am missing some basic information that makes this system unusable.
Thanks for reading such a long reply. and let me know if you have any objection to this idea
Glad you liked the article.
“Now in order to have grid tied or hybrid system you need to know that your utility company will buy the excess energy otherwise you will b dumbing this energy for free in the grid right?”
Unless you store the energy in batteries.
The way I understand your system it is scaled to never generate more electricity than what you need on a day-to-day basis and therefore you save money by not needing a big battery bank. I think it sounds reasonable, but a system like this could only cover a tiny of a household’s yearly electricity needs.
Dear Sir,
I want to buy two grid solar panel & inverter for office and residence. My requirement for home is 8 fans, fridge, 8 florescent bulbs, instant geyser. What will it cost. That it costs, guarantee, and after sales service will be available.?with regards,
Sincerely yours,
Sudershan Gosain
Hello Mathias,
regarding the grid tie in Poland,
Would it be reasonable to just install the standard hybrid system with a little more battery capacity and also divert energy to some usefull work that can be used later? for example a huge 100 gallon pre heat water tank.
Maybe you could supply free hot water to all of your neighbors instead of giving the grid free power!
Or any other use that would benefit people around you. Some kind of machine that does work like pumping water to garden area or extra air conditioning or heating in a room you usually don’t use.
Install a driveway heating system just for use when the sun is producing more than you can use. anything other than feeding back into the grid for free.!
Mathias,
I am in the beginning stages of designing a similar system. My intent is to build the system to charge a battery bank that I will attempt to build myself. I am gathering data now to build my own deep cycle batteries. The reason I am not going completely off the grid right away is that I do not know if I have enough South-facing rooftop to accommodate the required panel surface area. I figure if I make the investment in an automatic transfer switch I can use it now to backup my system with the public grid until I can afford to “grow” the solar setup and supplement with wind turbine power in the future, hopefully generating enough power to tell the utility company to piss off for good. At that point I will re-purpose the automatic transfer switch for a different type of backup power for emergency only. I reside in the Northeastern USA and have a small farm. Usually when the days are cloudy there is plenty of wind in place of the sun, making the turbines a natural choice. I have a good idea of my current load requirements, but as I build my system larger I intend to start using more electric appliances and eliminate the need for natural gas that I have now as well. I’m not sure about charge controller and inverter size. I currently have a 100A 110/220V service, but I will likely be upgrading to 200A as a part of this project. Please let me know if you have any recommendations for good equipment that I could purchase to make this system work. Thanks, Joe
Dear Shady Abeid,
i have posted some replies in this blog. Please view all of my replies and revert.
Regards,
Sudheer
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
@Shady Abeid: I also surfed the web to support your idea, but from my thinking (very very unprofessional) best connection is:
1) PV–>inverter –> power meter for solar plant –> grid
2) PV–>inverter –> after power meter of household –> home appliance
3) grid–> power meter of household –> home appliance
As you can see, there are two outputs of Inverter and home appliance has two inputs. Problem I see is that electricity can run from grid (3) into power meter for solar plant (1). There must be one way only connection and I doubt grid operator will allow that connection.
After all, grid operator loses two fees… one for distributing solar electricity from you and second is for distributing gird electricity to you… although you are buying back own electricity. Can somebody support that idea?
@MATJAZ,
In response to your comments to Shady Abeid, Most grid owners will definitely be loosing more and wont agree to this connection.
I have actually ventured into this area and believe me, you dont wanna go there.
Dear Matjaz,
please view my posts and revert to me. Once you read my posts you will understand that i have the similar concept as you mentioned.
regards,
Sudheer.
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
Hey Mathias,
great article and thank you.
I was wondering what do you suggest is the most expensive system component apart from the solar cells.
I feel batteries are expensive but I might be completely wrong. I would very helpful if you could enlighten me please.
Is there a solar system that runs like an off grid system that only utilizes the grid when the storage batteries run low? Not a battery back up system. Use battery power at night, solar power by day, and the grid only when your battery supply is low. Maybe a battery back up system could mimic this by just disconnecting from the grid at night effectively causing a “grid outage” causing switch over to the battery power then reconnecting to the grid in the morning. I am asking is there a setup that does this automatically?
Hi Mathiyas,
I am designing a Solar/Grid hybrid system with battery back-up for my home. My aim is to make solar is the primary source and the grid is the secondary source for my loads. Well, In my place power blackout occurs so often and here it’s not possible to deploy grid tied solar system. I don’t want to use the solar panels just to charge the batteries. I want to use energy from solar for my home appliances as well as charging battery banks also. The inverter should be able to disconnect the grid during grid failure. Can u please help me choosing the type of inverter and battery banks?
Fabian(India)
How to use the excessive ongrid solar power supply on holydays in india?
Hi
I’m an apprentice electrician in Queensland, the company I work for is looking for a system such as Johnny is asking about. With the current buying price of energy being so high and feed in price being so low, we need a system that can charge a battery bank for the house to use during peak hours, feed back to the grid once the battery bank is full and also connect back to the grid when the bank is nearly empty.
Dear Sam (from Queensland),
please read all my posts in this blog and revert to me at:
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
I have got exactly the kind of design your company is looking for.
Dear Shady Abeid,
iam working on a solar – mains hybrid UPS system and have got quite deep into the concept & design. Contact me at sudheersrivastav@rediffmail.com. Have a very brilliant idea which you would love.
regards,
Sudheer.
By the way guys reading this site:
by solar – mains hybrid UPS system, i mean:
a) When PV power is available, AC loads run on it.
b) When PV not enough loads automatically switch over to GRID supply and in case GRID supply not proper or no supply, the AC loads run on battery bank inverted to pure sine wave AC.
*All this switching is automatic and no user intervention required*
battery bank can be charged on PV power or GRID power, PV powering preference given to supplying load first and any excess power available will be used to charge battery bank.
sudheersrivastav@rediffmail.com
Dear Shady Abeid, Sudheer Srivastav and Apprentice electrician in QLD,
I am also working on some ideas to apply hybrid solar technology for our small wastewater treatment systems. Please contact me at struftepete@yahoo.com
Dear Sam from QLD, Marc, Shady Abeid from Poland and all others interested in this Solar – Mains Hybrid Power system:
Please contact me at the below mentioned mail id’s:
sudheersrivastav@rediffmail.com
Many people are requesting about this kind of system and are very enthusiastic about achieving this type of product implementation…
I have a very good concept and design.
I am an Electronics & Instrumentation Engineer with good experience in Analysis, Design & Implementation of Solutions for any requirement. I am also a Microsoft & Cisco certified IT professional. I have worked as a Project Engineer – Infrastructure Rollout/Management with 8 yrs of experience.
Other than that I am an avid researcher of Alternative Energy Technologies and Alternative Propulsion Systems.
By Alternative Energy Technologies, i DO NOT mean Solar/Wind/Geothermal etc (i have in my mind an entirely different concept of alternative energy tech) BUT at present Solar Power is the only Alternative Energy Technology which the alternative energy technology Suppressors will allow people to use because they consider that it cannot outrun people’s dependence on Oil & Gas as solar panels haven’t even touched the 50% conversion efficiency mark.
The reason why I am contacting all of you is because i want to design, implement and market a product which will make solar power a cost-effective viable option for everyone to use.
Presently the solar power products sold in the market demands a higher battery bank capacity for supporting larger loads for longer time and solar power is used ONLY FOR CHARGING OF BATTERY BANK and not powering AC loads directly.
“I don’t see any sense in converting solar energy to electrical energy, then to chemical energy by storing in batteries, and then back to electrical energy via DC-AC inverters”
Grid-Synchronous Solar Inverters are not great because as per the regulation laid down by Power Companies, they must power down when the grid supply fails….which means they can’t be used when grid supply is down…this contradicts the very meaningful usage of solar power!
I have searched all over the Internet and the above mentioned systems only are sold. I have tried contacting some mass production centers in Mainland China for mass producing my concept according to the excellent design specifications i have made, but none are yet up to the point of being able to understand the efficiency of the direct energy conversion system such as the one I am talking about.
Then I searched more vigorously and found this blog and i am thrilled that I am not alone in this thought process of wanting to make a high-efficiency direct conversion solar power system.
I am looking for like minded professionals/Organizations/VC’s who are interested and very serious about this Solar-Mains Hybrid Energy System design, development and marketing on a very large scale basis and also exporting the product to other potential markets across the world.
“WE NEED TO DECREASE THE DEPENDANCE ON THE FOSSIL FUELS/GRID POWER FOR THE SAKE OF REDUCING OUR ELECTRIC BILLS AND ALSO TO MASSIVELY REDUCE THE POLLUTION DUE TO BURNING OF FOSSIL FUELS FOR GENERATION OF ELECTRIC POWER.”
I have a very good concept for the Solar-Mains Hybrid Power System to design it from scratch and I also know the exact parametric design methodology to ensure the highest possible efficiency and cost-effectiveness of this system.
(High-efficiency Inverter design, precise Solar MPPT design, fully automatic transfer between solar/grid/battery operating modes, Load Detection & Management to restrict battery bank size to bare minimum, battery chemistry suitable for solar and design of charger suitable for most efficient charging etc)
I am eagerly waiting for a response.
Regards,
Sudheer
Thanks for sharing. The way illustrated is really fantastic and informative to know.
Hallo guys
I have moved to south africa where laws on grid-tie not are like in europe. we are not allowed to feed electricity back to the grid at all. So people build stand alone systems. Im trying to find an inverter with an intern switch, that can use my power from my panels and batteries. And when night falls it must be able to switch to the grid automaticly. But never feed electricity back to the grid. Can anyone show me a website with that kind of inverter?
You can also check this link to see what i mean. The only problem with the picture on this link is that the system feeds overproducing electricity back on the grid. http://www.clevertec.co.za/Figure_2.html
Regards
Christian
Hey Christian,
Google the thing dude! South Africa is one place which adopts latest technologies much quicker than the rest of the world….so the kind of thing you want would surely be available there. Here’s one link which has a Solar UPS with a AC transfer switch….which means it transfers load between AC mains and Solar power.
http://www.bluesunenergy.co.za/products.php?catID=22&cat=UPS/SOLAR%20UPS
What you need is a “DC to AC Inverter with LOAD TRANSFER Switch”
Hi Christian,
i am also in SOuth Africa and i use a Bi Directional inverter to do just that. My panels chanrge my batteries and run half my home, if the batteries go to 30% DoC then the inverter switches automatically over to Eskum..
Everyone reading this Blog,
First of all we have to says Kudos to Mathias!
If not for him having taken time to create this blog and give the information which created interest in folks like us….all this information exchange and discussion would not be taking place.
Thank You Very Much Mathias.
regards,
Sudheer
sudheersrivastav@rediffmail.com
Hi, i am looking for Solar Off grid inverter from countries within europe also as per european standards,the range is from 1KW – 10KW.So can you refer any reputed company.
Hi Vinod,
are you looking for solar inverters to install them for customers in europe or do you want to import solar inverters from europe? where are you located? Have you considered the fact that a solar hybrid system is way much efficient and extremely cost-effective than a pure off-grid system?
regards,
Sudheer.
sudheersrivastav@rediffmail.com
Hi Mathias, Shady Abeid, Sam, Matjaz and everyone
“WISH YOU ALL A VERY HAPPY NEW YEAR”
I am feeling very enthusiastic about 2013 and hoping that the need for designing a direct conversion solar mains hybrid power system will be felt more than ever. I am calling upon all those people/professionals with advanced electronics knowledge and those electronic design engineers with access to high-end electronic CAD simulation software to achieve this goal. I am hoping for a good response in this year 2013.
Regards,
Sudheer.
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
Dear Sudheer,
A VERY HAPPY NEW YEAR TO YOU.
The concept you had in mind is one of the best what Indians need at this time.
I live in Andhra Pradesh and I am very much interested to know more about your concept of
PV to loads, in case of inadequacy of PV then Grid and in case of Grid power cut then battery bank to loads.
If you have developed a suitable inverter or know about someone who has one of this type, I request you to share the same with me.
Thanks
RAMMOHAN
I think the Outback “Radian” series of inverter would work for this application….only drawback I can find is that the battery bank should be close to the inverter itself – don’t think my wife would go for batteries in the family room….
Everyone is talking about storing excess solar electricity in secondary electrical cells but there are other ways to store energy. There is a solar thermal power plant in Spain that collect solar energy using parabolic troughs that are focused on oil filled tubes, the hot oil is then used to produce steam or to heat molten salt, storing the heat for later use. Other ways that utilities store electricity is to use it to pump water up to a higher elevation and, when the energy is needed, let it flow back down through a turbine. There is also mechanical storage using flywheels or as a pressurised hydraulic liquid or compressed gas. Or, in my opinion, converting the electricity into a storable, chemical fuel that can then be used in a engine, such as Hydrogen through the electrolysis of water, however H2 can be difficult fuel to store and use, so, better yet, use the H2 to produce Methane, the chief component of Natural Gas & Biogas, a fuel made to the rotting of organic matter in low-O2 environment, by combining it with CO2, for the Biogas, for example, using the Sabatier process. H2O produced during the process and the combustion of the Methane can go back into the electrolyzer and the CO2 can be recycled through the process. Oxygen produced during electrolysis can be either dumped or used to combustion of the Methane in a pure O2 environment, lowering NOx emissions
unable to post reply….some error creeps up saying:
“we cant find the page you are looking for, press back button or goto homepage”
Hi Sudheer,
Did it work for you now?
Hi Mathias,
i am glad to receive a message from you. Well i don’t know the exact reason( maybe it’s a character limit, paragraph limit or something) but i am not able to post my complete reply to those reading this blog and asking if i made an inverter or know someone who made it. Till now i have been able to post only half of my detailed reply.
I am trying to make people understand of the new concept of direct energy conversion to avoid huge battery bank and also hoping to get in touch with electronic design professionals (such as shady abeid) with access and expertise in electronic CAD simulation software, so that i can come up with a solar-mains hybrid power system which is 98% efficient and does the required job.
Hi Sudheer,
You should be able to publish the entire comment now.
Regards,
Mathias
Dear All,
I would like to clarify something. I am receiving many emails and posts asking me if I made some inverter or if I know someone who made it.
First of all I would like to point out that the word “Inverter” is being used very loosely. If by that you mean a large black box which hooks on to a couple of batteries and wires run to the mains panel in your home and it beeps when there is a power cut…..NO IAM NOT MAKING THAT AGE OLD INVERTER STUFF.
What I made is a SOLAR-MAINS HYBRID POWER SYSTEM. Please don’t call it as an Inverter or compare it with the crappy inverter stuff available in market.
My device has the following sectional blocks:
1) Solar Panel Array Output Conditioner: This is the first section which takes the varying output from Solar Array and makes sure that it’s steady and the maximum possible power is being drawn from the solar panel at any given time between reasonable limits of Dawn & Dusk. (Maximum Power Point Tracking)
2) Second stage is an Inverter circuit (it is an IGBT based electronic inverter circuit. Don’t confuse the word “Inverter” with a big box sold in the market and which is hooked to batteries).
The inverter stage is unlike ordinary ones and accepts different range of voltages from either a solar array output conditioner or battery bank. Normally you would need 2 inverter stages (which increases cost significantly) one for solar array and one for battery bank but I figured out a method to merge both together into one single module/section to reduce cost and duplicity of components.
3) Third stage is a microprocessor based precision battery bank charger which also alerts if there is a failure in battery bank. You need to write a program in “C” or better in Assembly Programming Language for that microprocessor to execute commands faster.
4) The fourth stage is a Load Control and Management circuit. It senses when the solar array output is enough to run the LOAD and connects the LOAD to it. When solar output drops or load increases beyond solar output handling capability, it connects LOAD to MAINS. When both solar and grid power are not available, the MINIMAL BATTERY BANK powers critical loads such as computer etc. Also this system is designed to run few ceiling fans and tube lights etc overnight. Let’s say there is a power cut from 10PM tonight till 7AM next morning….you can have at least two ceiling fans running for a comfort sleep with a minimal low cost battery bank.
So in my design, there is no huge battery bank stage. Hence it is a direct energy conversion system which is the best possible for a low cost solar-mains hybrid power system. Currently I planned this system to be able to provide upto 4kW of power. So it will be able run LCD TV’s, Refrigerators, Ceiling Fans, Tube Lights and Washing Machine etc simultaneously upto 4kW max. Minimal battery bank will provide backup only to smaller loads like ceiling fans, LCD TV, Desktop Computer etc and not to washing machine or refrigerator. All this segregation of large inductive loads and critical loads will be taken care of by the device without any human intervention.
I have a design which is about 75% efficient. I am trying to select new and latest components from various Semiconductor and Power MOSFET manufacturers…..trying to simulate the revised versions with electronic CAD simulation software and come up with a final version of the device which has a 98% efficiency. The Electronic CAD software are expensive (USD 5000), there are many simulation models file formats and I need to have access to these to get the job done. The only person in this forum who claims to have run simulations has still not responded to my messages to him and neither do I have his direct contact details.
If anyone can search and find a device in the market which does exactly what I described above….please be my guest. I’ve been searching for more than 3 months and I am sure no such device is available in the market…that was the reason why I took up this project. I have already mentioned in my latest post that I am expecting response from electronic design professionals having knowledge and access to such software’s so that I can come up with the final solution after running simulations using those software.
I have no argument with those who mailed me saying:
“We can buy solar panels, an Inverter, a battery charger which are commonly available in the market and assemble them all to make the device you are talking of”
Well if anyone can just buy those individual devices and hook them up and do exactly what I said for USD 300-500 (excluding cost of solar panel array), with an efficiency of 98% and not to mention the complete automated load segregation and management (0% human intervention), once again please be my guest.
Guys, I am struggling to get access to those expensive high-end software, be able to open all those various electronic components simulation model file formats from different manufacturer websites and run those simulations to achieve a final revision with 98% efficiency! Any help will be deeply appreciated.
sudheersrivastav@rediffmail.com
I have a off-grid hybrid wind and solar system. Is there any possibility to convert a off-grid to a on-grid system
Dear Manuel,
what exactly do you mean by off-grid to on-grid conversion?
If you mean that once your off-grid battery bank runs out of juice, you would like the system to revert to using grid power. Yes, that can be simply done.
All you need is a 110 or 230VoltAC DPDT(Double Pole Double Throw) Power Relay rated for your total load amperes.
I don’t know how to post a circuit diagram here but will be glad to email it to you.
Brief Explanation:
Your off-grid Inverter “Live” and “Neutral” terminals are connected to this Power Relay Coil and also to one contact each of the double poles. Grid Input’s “Live” and “Neutral” terminals coming from your house circuit breaker are connected to the other two respective poles. The “LOAD” is connected to the common terminals of the relay poles.
(THOUGH THIS IS A SIMPLE TASK, I REQUEST YOU TO TAKE HELP OF QUALIFIED ELECTRICAL PERSONNEL TO DO THIS WIRING TO PREVENT RISK OF SHORT-CIRCUIT AND DEATH/INJURY)
When your off-grid inverter is supplying power, the relay coil is energized and connects your house “LOAD” to itself. When your off-grid Inverter stops because battery bank ran out of juice, the relay coil is de-energized and “LOAD” gets connected to Grid Mains Input. This means 0% human intervention.
(ALWAYS TREAT ELECTRICITY WITH RESPECT OR ELSE IT MIGHT GET YOU KILLED)
Here is a link for the relay:
http://www.rapidonline.com/Electronic-Components/DPDT-10a-Power-Relay-230v-Ac-60-1676
You can buy one from Ebay or preferably from a local electrical & hardware store.
regards,
Sudheer
sudheersrivastav@rediffmail.com
“IS THE BENEFIT OF HAVING A GRID TIED (GRID SYNCHRONIZED) SOLAR INVERTER ONLY THAT WE CAN FEED BACK POWER TO THE GRID AND ENJOY NET METERING BENEFIT?”
Dear All,
It’s been a while since I posted new information. I was off the blog due to some critical work and was busy researching and figuring out the best converters and charger topology/configuration solution for the solar project.
I’ve been receiving emails about solar inverters and I see a lot of confusion about their types, benefits and which would be the best for our present day application. There are basically three types of Solar Inverters:
1) Off-Grid Inverter
This is the traditional inverter type which has a solar charge controller charging a “LARGE BATTERY BANK” that supplies power to a DC-AC inverter which enables us to run AC loads. So there is an “INTERMEDIATE STEP” of solar to chemical energy conversion involved in this process. The batteries are always involved in the energy conversion process. This type of inverter works only as long as the batteries have some charge left in them. There is no connection to the GRID and this system goes dead once “Low Battery” is reached. The large battery bank (MOST EXPENSIVE PART OF THE OFF-GRID SYSTEM) is a necessary evil to ensure a steady/smooth output from the Inverter to the AC loads even under a significantly varying Solar Irradiation condition.
2) On-Grid Inverter
This is the same as an off-grid inverter but a simple DPDT (Double Pole Double Throw) AC Power Relay is connected at Inverter output and as soon as “Low Battery” is reached and Inverter shuts down, the AC Loads are re-connected to the GRID. This way the LOADS have an uninterrupted supply of power and chances of total blackout is quite less.
In my last post dated: February 12, 2013 @ 10:47 am, I have explained about this arrangement for the simple automated switching without human intervention.
3) Grid Tied (Grid Synchronized) Inverter
Here comes the most interesting part of solar power harnessing to get usable 120/230VAC electric power. The Grid Tied Inverter has its OUTPUT synchronized to the FREQUENCY (exactly same), PHASE (exactly same) and VOLTAGE (slightly higher for feeding power into GRID and also powering the LOAD) of the GRID. The output of the Inverter and Grid Supply are literally paralleled and connected to the Load.
“WHAT IS THE BEST BENEFIT WE OBTAIN FROM SUCH AN ARRANGEMENT?”
Let me cite an example to you. Say we have a 4.5KiloWatt Peak Solar Array which is connected to a Grid Synchronized Inverter. Let’s assume its 7:30AM in the morning and you are using a LOAD of 1.8KiloWatt. Also let’s assume that the Solar Array is able to provide just about 600Watts of power at the time of day. Without a large battery bank as in an off-grid system, we cannot simply run the LOAD on PV alone isn’t it? But a large battery bank is pretty expensive in terms of initial cost and maintenance/replacement batteries cost. So this Grid Synchronized Inverter eliminates the large battery bank and the associated “Prohibitive Cost” and poor “Solar to Electrical Energy Conversion Ratio” of the off-grid system.
It also does a great job by letting us use that little amount of 600Watts of PV power to partially run our 1.8KiloWatt Load, the rest being “SUPPLEMENTED” by the Grid. As the Sun moves across the sky and more PV power is generated, the lesser utilization of the Grid to power that 1.8KiloWatt Load.
What I am trying to say is that no matter how much little the power output of Solar Array is, WE CAN BE SURE that it is EFFICIENTLY HARNESSED and USED to the MAXIMUM EXTENT. Since the GRID is an Infinite Voltage Source, the LOAD will never experience a blip or brown-out due to the GRID SYNCING operational topology. You wouldn’t want you LOADS to be blinking/flickering with just a slight change in Solar Irradiation, isn’t it?
But there is one problem with Grid Synced Inverters, which is:
As per UL1741 directive, Grid Synced Inverters must shut down within 100millisecs of Grid Failure or disconnection at transformer. This is a safety requirement for maintenance and troubleshooting personnel. This is an important PROTOCOL to follow but if a Grid Synced Inverter stops supplying power to your Loads when Grid fails or is stopped, it wouldn’t be a great topology to use, isn’t it? So we have to find a workaround (which is what I’ve planned and have a decent idea in my mind) to be able to follow the PROTOCOL as well as keep the Loads powered.
And last but not the least, as Mathias explained way back in his article, it would be great to have a Grid Tied (Synchronized) Inverter with “BATTERY BACKUP” to make it the most suitable, efficient and cost-effective solar power system.
regards,
Sudheer
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
Hi Sudheer,
I am currently working for a University in Australia on a hybrid systems that will intergrate PV panels, batteries and the grid. Im very interested in this idea of Grid Synchronized Inverter that you mentioned.
However I was just wondering what happens to any excess electricity that might be generated during the day and not used i.e does the excess energy go back to the grid or would it simply go back into a battery bank or not be used all?
I think this is a fantastic idea if it can be made to work if the grid fails and power is lost. If a battery backup can be implemented for these times then I think the idea is very plausable.
Hi Tim,
When the load consumption is less than energy production, it will always be fed back to the Grid for net metering and battery bank will also be kept charged. Otherwise the daytime working couples and their school going kids won’t be happy with my design, isn’t it? There will never be a time when the panels are producing power and are left idle. The only way this can happen is when the consumer is on a long vacation and the grid too has failed for a long stretch of time…..both of these happening TOGETHER is an unlikely event.
regards,
Sudheer
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
Hi,
backgroud….
I have a project where the current is only needed during the time the sun is bright to produce enought power to facililate the need (so i dont need to charge batteries). There is no grid power available in the area or if i need to get grid support its going to sooo expensive.
For my understanding the off grid converters are not that efficient as the grid ties. (or the ones which i can afford). Also the new trend is grid ties and such converters are easy access for me. The grid tie converters need the power source to be present to start work.
my questions is as follows….
Is it possible to get a low watt (50 – 100W) off grid converter and link with few grid tie(1000W x 5) inverters together?
The grid ties would detect the output of the off grid and tigger to create the final out put i need.
I know that grid ties can be combined together. Are the off girds have the same possibility..
can my idea be practical??? please help
i want to take it for my final year project…plz guide me,,
I have been researching an off grid system that is capable of feeding AC directly from the inverter and at the same time be able to charge the battery bank. i,e direct AC voltage day time and use battery bank night time. (plus a diesel generator back up )with this system i am totally independent.
Xantrax has hybrid inverters, capable of inverting and charging the battery bank, i wil encourage some folks to review it
Hi,
it looks like the webpage has been modified but the indication of the number of comments is not displayed.
Also it would be nice to have an optional feature which sends an email alert if a new post has been placed or if someone replied or responded to your post. I hope its not too much to ask.
sudheersrivastav@rediffmail.com
sudheersrivastav.s@gmail.com
We`re changing the design because the old one was too inefficient. Should be finished in a few weeks. Will look into the email feature that you are asking for Sudheer.
Thanks!
Hi all,
I have a question to ask regarding connecting load to my solar system. if I connect my DC to AC inverter directly to my Mppt charge controller, will it regulate load current also as it regulates current from PV array.
what I understand is, if I do so, my charge controller (combined with inverter) may act as “solar hybrid inverter”.
i mean when solar energy is available inverter will take input directly from PV array instead of using batteries and extra energy will be stored in batteries by charge controller.