Are you considering installing a solar PV system? One crucial component you’ll need to decide on is the type of inverter.
The basic function of an inverter is to convert the direct current (DC) electricity generated by your solar panels or drawn from your batteries into alternating current (AC) electricity, which is suitable for use in your home or business.
Let’s start with the clearest delineation – string inverters versus microinverters.
String inverters – receive DC output from multiple solar panels (often your whole solar array or at least a ‘string’ or two) and convert it to AC electricity. It is a single large(ish) component usually mounted near your distribution board (although certain systems will call for multiple string inverters).
Fronius Gen24 ‘string’ inverter
Enphase IQ8HC microinverter
The commonly held view has been that microinverters, when compared to string inverters, generally perform better, particularly if one or some of the panels are shaded, last longer and are safer. However, the latest string inverters, such as the Fronius Gen24 range, have very high performing maximum power point trackers (MPPT), which were found by a recent French study to perform as well as microinverters. These modern MPPTs even minimise the power loss across an array if there is shading on some of the panels to the extent that there is little to chose from between a microinverter system and a string inverter system.
The argument that they last longer is also generally discounted nowadays on the basis that they are both inverters and it really just comes down to the quality of the built by the manufacturer. Therefore, there is no particular reason string inverters from reputable manufacturers such as Fronius and Victron shouldn’t last as long as an Enphase microinverter. However, if a microinverter fails, it won’t take out the whole system, whereas a string inverter likely will. However, there is still a high likelihood it is simpler to get a string inverter repaired as it is usually at ground level, easily accessible and may only need a component replaced. With a microinverter, you will need to locate the problematic unit in the array, potentially requiring removing part of the array, and then install a new unit.
In New Zealand the warranties for Fronius string inverters (provided you register the inverter with Fronius) and Enphase microinverters (by far the most common microinverter brand) are both 10 years.
If the ability to expand your system is a key design requirement, microinverters are likely worth considering. As each panel effectively becomes its own little power station, feeding AC electricity, expandability can be more straightforward. However, as is usually the case, it depends on the situation. There can still compatibility issues with microinverter controllers and the like, and in many scenarios, especially with a bit of planning when the first phase of the installation is designed, it may be easier and cheaper to expand a system using a string inverter.
One notable upside to microinverters is that the electricity moving around is generally AC electricity, rather than DC electricity, which is safer. This is a consideration although modern string inverters do limit this risk through systems like Fronius’ Arc Fault Circuit Interruption (AFCI). There are also regulations in place to make sure the cables carrying DC cable are well protected and this part of the installation is a focus of the independent electrical inspector, who is required to inspect all solar installations.
Another advantage of microinverters is that the panels do not all need to be aligned the same way. A single MPPT requires all panels to be in the same alignment (both angle and pointing in the same direction). The likes of a Fronius inverter only has two MPPTs built into it so you can only arrays in two different alignments feeding it. Other manufacturers such as Victron, while they use string inverters, do not generally build in the MPPTs, producing these separately so they can be sized for the number of panels in a given array/on a given aspect. However these can multiply up quickly and create a complex power wall. Microinverters incorporate individual MPPTs so are a great solution if a installation calls for small numbers of panels (say 1 to 4) on lots of different aspects (three or more).
Victron Multiplus-II inverter. This inverter does not include a MPPT, instead it requires a standalone MPPT ‘solar controller’ such as the one below, to be incorporated in a solar installation.
Victron MPPT SmartSolar 250/100 Solar Charge Controller. This is a standalone MPPT that works with the likes of a Victron Multiplus-II string inverter.
The major advantage of string inverters is price and simplicity. The reality is that for the vast majority of installations undertaken in New Zealand, the advantages of microinverters are very limited when compared to modern string inverters (and MPPTs) and do not justify the additional cost which can result in the system costing as much as 50% more.
A basic inverter function is to simply convert a particular voltage of DC electricity (usually 12V, 24V or 48V) to AC electricity (230V for regular NZ usage). It does not have a MPPT and therefore needs a separate solar charge controller, such as the Victron SmartSolar Solar Charge Controller above, to manage the ‘raw’ output of the PV solar. It will then take the DC output of the solar charge controller or the battery and convert it to AC for use in your household or business. It only has an AC output, not an AC input, and therefore cannot charge a battery from an AC power source such as the grid or a generator.
An example of this type of inverter is the Victron Phoenix range of inverters.
An inverter charger is similar to the basic inverter above in that it doesn’t have an in-built solar charge controller, but it will have at least one AC input. This allows it to take power from an AC source such as a generator or the grid and charge the battery. This is a requirement in most off-grid systems with a back-up generator and in grid-tied peak shaver systems that charge the batteries from the grid to provide back-up capability from battery, shift import of power to times with cheaper tariffs or provide additional capacity to a system for high demand periods (i.e. if power demands at certain times are higher than the the supply current, in NZ most single phase residential systems have a supply limit of 63A).
Examples of inverter chargers are the Victron Multiplus, Mulitplus-II and Quattro ranges.
A hybrid inverter is a string inverter (i.e. an inverter that has the MPPT to allow it to manage the PV solar) that can also integrate with a battery. Hybrid inverters are often quite particular about the batteries they will integrate with but, for many people, it gives a great, streamlined system.
A hybrid inverter will also synchronise with the grid and meets the regulations to be compliant to be connected to the national power grid – the relevant regulation for whether you can have an inverter connected to the grid in New Zealand is AS/NZS 4777.2.
Examples of hybrid inverters are the Fronius Gen24 Plus inverters and the Victron EasySolar range.
Ultimately, the best inverter for your solar installation depends on your specific needs and situation. For the majority of grid-tie installations, a string inverter or hybrid inverter will be the best, most cost-effective solution but there is definitely a place for microinverters and inverter chargers in certain systems. In off-grid systems, inverter chargers come into their own, but there are significant loads while the PV solar is producing (e.g. a spa pool or EV charging), including an efficient string inverter such as a Fronius Gen24 inverter in the system may still make sense.
By carefully weighing the factors and consulting with a professional solar installer, you can choose the inverter(s) that best meets your requirements and optimises the performance, cost-effectiveness, and longevity of your solar system.
Investing in solar is a significant decision, and selecting the right inverter is crucial to ensuring that your system performs at its best.
Posted in Miscellaneous
New Zealand is a windy place and any systems out there at the mercy of the elements, wind or solar, must be capable of coping with our harsh environmental conditions. Current Generation supply Pinnacle wind generators. If you’re thinking of investing in a small wind turbine to generate electricity, here are some answers to some of the most asked questions.
Wind turbines are a clean and efficient method of turning raw kinetic wind power into electric power.
Wind turbines can be connected directly to machinery for mechanical energy, or they can be connected to power generators and can create electricity. These three bladed structures, mounted on high poles or towers, are typically pointed into the wind using computers and sensors.
The wind turbine itself is made up of a rotor mounted to a wind turbine generator which is mounted to a frame and then a tail is mounted on the opposing side of the rotor.
If the wind turbine does not have a sensor-based system pushing it into the wind, the tail will adjust it manually. Higher towers and broader rotors will generate more energy overall, so if you are considering the investment, understand that it is long term outlay and that the relatively low additional cost for a higher tower or larger rotor on your wind turbine will help offset the overall cost more quickly.
As you consider your investment in a wind turbine generator, consider a hybrid power system using solar electric panels as well. Depending on where you live the seasonality of wind speed and the amount of sunshine produced in the warm summer months, you may find that you’ll reap more benefits from using all of your natural resources to power your home rather than just one or the other.
A basic wind power system will consist of:
Wind turbine on top of a tower (1) that is wired down to a control box (2) that regulates the charging of a large deep cycle battery bank Inverter which draws electricity from the battery bank and converts to normal household electricity (AC) & feeds the appliances in the home with power as needed.
Various safety devices like fuses, breakers and lightning arrestors
Free energy for renewable energy installations comes mainly from the sun and the wind. Wind turbines are the ideal partners for solar panels because when the sun is not out during the day, the wind is usually blowing if you’ve got a good wind turbine site. At night there is no power from your solar panels, but it is often windy. Wind turbines are also cheaper than solar panels for the same power output, although the overall cost of the energy installation must be considered.
This depends on how much energy you need, and how much is available from the wind at your site.
Evaluating your energy requirements is not too hard – it focuses on the various electrical appliances you have, how much power they use, and how often you use them.
If your intended site for the wind turbine is up on a hill or a ridge and/or is exposed to high prevailing winds, then there is a good chance that much of your energy can be supplied from the wind turbine.
Renewable energy installations for homes often have a 1 kW wind turbine that has a rotor that can be anything from 2.1m to 3.6m in diameter.
If you have larger energy requirements and you have a good wind resource, then a turbine might suit.
A windy place on your property is the obvious choice, but carefully consider the options before deciding on the best spot.
For example, although the edge of a cliff on a coastal property might be windy, don’t put your wind turbine there because abrupt changes in the landscape makes the wind do strange things and can adversely affect your wind turbine’s performance.
In general terms, a site that has at least a half-acre of open land and average of 10 mph (16km/h) or higher winds is a good candidate for a wind turbine installation.
Pine trees can grow quickly, so don’t erect a turbine amongst young trees As a general rule, an exposed and elevated site with gentle surrounding contours (preferably flat) is the best.
Distance between your wind turbine and your house will vary from site to site, and there are ways of minimising the losses in your cable connecting the two, depending on the specifics of the machine you buy and your application.
Check with your local authorities for their requirements regards, height, distance from dwelling etc too!
Noise is an issue for some people, and not for others.
It is subjective. If you are intending siting your machine close to your home and are worried about the noise, then buy a machine that is designed to be quiet. In many cases you won’t be able to hear it no matter how noisy it is, because the wind itself creates noise around the house, trees and so on, or the machine is sited far enough away from your house. Don’t be tempted to attach the wind turbine directly to your house, no matter how easy it looks to do. The vibrations and resonance from the turbine will keep you awake at night.
When considering renewable energy options for your home or property, you may be wondering whether wind or solar power is the better choice. Both have their advantages and can work well together in a hybrid system.
Here’s a comparison of wind and solar energy to help you make an informed decision:
Both wind and solar power have their strengths and can be effective renewable energy sources. The best choice for your property will depend on factors such as your location, available space, budget, and energy requirements. A hybrid system that combines wind and solar can offer the benefits of both technologies, providing a more reliable and consistent power supply.
This article was originally published on Solar Quotes, the original post can be found here. So, what is a kW & a kWh?
And what is the difference between a kW and kWh?
An older style meter showing kWh
Let’s start with what each letter stands for:
So kW means kilowatt which is 1000 Watts, a measure of power.
Notice that, if you like to keep pedantic electrical engineers like me happy, the correct way to write it is always with a small k and a capital W.
The size of a solar system is defined by its peak power, often denoted as kWp (the p standing for ‘peak’), e.g. a 1 kWp system can produce 1 kW of power per hour when operating in line with the testing parameters.
kWh stands for kilowatt-hour; a kWh is a measure of energy (not power).
If your solar panels (for example) continuously output 1kW of power for a whole 60 minutes, you will have produced 1 kWh of energy.
The amount of electricity you use (or generate) is defined in kWhs. e.g. “My solar system produced 4 kWh of electricity today!”
So at the highest level: kW measures power, and kWh measures energy.
Why is the difference between Energy and Power important?
It is very common for people to mistakenly interchange the terms energy and power as if there is no difference. Most people do it all the time without noticing. It drives electrical geeks up the wall.
For example, if someone is talking about their electricity usage and says, “I used 8kW yesterday”, they probably mean that they used 8 units of electrical energy yesterday. In this case they should really say, “I used 8kWh yesterday”
Yeah, yeah I know what you are thinking: Who cares?
Well it is actually quite important if you are buying a solar system. If someone says they need a solar power system to produce 8kW, they might end up being quoted an 8kWp solar system. Which will cost about $24,990 + installation at today’s prices and produce about 32kWh per day.
If, what they actually meant was that they need one to cover an energy usage of 8kWh per day, then they really need a 2kW solar system which costs about $8,375.00 + installation at the time of writing!
So please don’t confuse kW and kWh. If you do you may end up with a solar system that is completely the wrong size! Top tip for filtering out the worst solar salesmen: Ask them to explain the difference between a kW and kWh. If they get this wrong how on earth are they gonna understand your requirements? A lot of cold calling door knockers will fail this test in my experience. The technical bit for those that are interested:
Is Your Roof Right for Solar Power?
Solar power is a fantastic way to reduce both your electricity bills and carbon footprint, particularly in regions like Nelson, Tasman and Marlborough which are known for their high sunshine hours – but not every roof is suitable for solar panel installation. If you’re thinking about adding solar to your home, here’s a guide to assessing if your roof is suitable for mounting solar panels.
The first thing to look at is the angle of your roof. The optimal angle for solar panels is generally equal to the latitude of your location to maximise sun exposure throughout the year. For example:
If your roof angle differs from these ideal conditions, don’t worry too much. A deviation of about 10° from the ideal angle typically results in less than a 5% decrease in power output. In New Zealand, typical roof angles are between 15° and 35°, which are generally sufficient for effective solar energy generation. If your roof is flat, consider installing tilt racking to position the panels optimally. Despite the additional cost, the additional output from mounting your panels at a more optimal angle with typically result in a short pay-off period.
The next thing you should consider is the direction that your roof is facing. In the Southern Hemisphere, a north-facing roof is perfect for solar installations. While north is ideal, technological advancements and reduced costs have made east or west-facing roofs increasingly viable. In New Zealand, where sunlight is abundant in many regions, an east or west orientation can still harness significant solar power. In fact, this may work well with your daily energy usage profile, providing good output earlier and later in the day when your demands are higher.
Previously panels needed relatively direct sunlight to produce a meaningful amount of energy, nowadays the technology has improved such that even south facing panels will provide reasonable production; similarly you’ll see production on overcast days. As an example, and this is not to suggest you mount your panels facing south(!), on a 15 degree southerly facing roof in Hobart, Tasmania (which at 42.9 degrees latitude, is south of Nelson) a panel will still provide 74% of what it would if mounted in the ideal direction over the year. However, it is worth noting the winter production will be fairly abysmal, generally only about 40% of their north-facing counterparts.
Today, the improvements in PV panel affordability also helps provide a solution. Where roof aspects are not ideal for all-day sun, it is often worth adding a couple of extra panels (so-called ‘over-panelling’) to get the most out of your system. This works very well where you have panels facing multiple directions (e.g. NW and NE) as it provides more consistent output throughout the day, as opposed to their being a large peak in the middle of the day.
The last one, the biggie… is shading. If any shade falls on your roof, then you must quantify whether that is going to be a problem – or how big of a problem it is going to be. Shading is a critical factor that significantly impacts the effectiveness of a solar installation. If trees, nearby buildings, or other obstructions cast shadows on your roof, it’s essential to conduct a detailed shade analysis. We generally work with 16 degrees being the angle above which we want to avoid any substantial objects that may shade the panels; this equates to the mid-winter sun angle at 10am.
Occasion shading of a small part of an array on a string inverter is not such an issue nowadays as it was in the past. Where in the past, microinverters were often used to manage potential shading by effectively individualising the management of the panels so shading on one panel wouldn’t effect the production of another, panel and solar controller technology has improved significantly meaning it will only limit the production from the shaded panels (and possibly only the shaded half). This improvement has meant there is generally less call for microinverters in installations than there once was.
Determining whether to install solar panels on your roof isn’t just about having the perfect conditions; it’s about making the best of what you’ve got. Most roofs, while not ideal, can be adapted to significantly boost their solar viability. This is where a skilled solar installer becomes invaluable. They won’t just look at your roof and see an angle or orientation; they’ll see potential.
By carefully assessing the specifics of your roof’s angle, direction, and shading, a seasoned installer can provide you with a detailed analysis of what to expect in terms of energy production. They’ll give you the hard numbers on potential power output losses and weigh them against the benefits of going solar. This means you won’t be going in blind; you’ll have all the facts you need to make an informed decision.
Remember, if your roof isn’t viable, there may well be the option of a ground mounted solar array, so all is not lost. One advantage of ground mounted arrays is that you can generally position them to face the ideal way, at the ideal angle and avoid any shading.
For homeowners in New Zealand, considering these factors can help maximise the benefits of solar installations, allowing you to tap into the renewable energy market efficiently. This proactive approach not only supports the environment but also aligns with New Zealand’s goals for sustainable development and energy independence. By overcoming the usual hurdles associated with residential solar power systems, you not only contribute to a greener planet but also invest in long-term savings and energy security for your home.
Should you put your panels on tilt frames?
Tilt frames are used to get solar panels to the optimum angle and maximise power output.
Here is really common dilemma:
“I’ve got 3 quotes for solar: The first company says my roof is at the wrong pitch and wants to charge me hundreds of dollars extra to put my solar panels on tilt frames to optimize the amount of electricity I get. The second mob say it is fine to just put the panels flush on my roof and the third guy says that, yes, my roof isn’t at the perfect pitch, but the best solution is to mount them flush to the roof and simply add an extra solar panel to make up for any reduced power output.
Now I’m really confused! Help!”
The problem here is that there are two extremes of solar installers:
At one end of the spectrum, you have “The Solar Purist”.
They are only happy if the solar panel is positioned for the absolute optimum power output – they are a perfectionist, highly technical, and have been in the industry since the dawn of solar, when solar panels cost 10 times what they do today. They think a few hundred dollars is a small price to pay to squeeze a bit more power out of those precious solar panels. And please, never, ever suggest to them that they use a non-German inverter.
Then at the other end of the scale – you’ve got the “She’ll Be Right” Solar Installer.
They just want to get the install done. If you’ve got a roof, and it doesn’t face south, and it’s not completely shaded they’ll bang the panels on and move on to the next job.
We believe that the best installation for your home is somewhere in the middle.
The best solution to maximize return on your investment.
You need to consider the financial consequences for each option and then decide whether tilt frames are a good investment or not.
So, let’s look at a typical scenario where tilt frames would be an option and see which of our 3 original options makes the most sense from an economic perspective:
To Tilt or Not to Tilt – that is the question
How to work out if tilt frames make sense or not:
Imagine you have a house in Nelson and you want to install a solar system. The house has a North facing roof that has a very shallow slope of 10° and you want to install a 3kW system. The perfect tilt angle for solar panels is the same as the latitude of the install location. Nelson has a latitude of 41°.So therefore the panels should be of the Latitude.
So, if we follow those guidelines, we’d have to use tilt frames for all our solar panels, right?
Panels at the perfect Angle:
If we crunch the numbers, then we can quickly work out that 3kW of north facing solar panels at the perfect angle of 41° will produce 12.0kWh per day averaged over 1 year. If we value our electricity at 25c per kWh, then that earns us $1095 per year.
Panels at 10° If we crunch the numbers for 3kW of North facing solar panels at only 10° then we discover that we get 11.6kWh per day which makes us $1058.
How much do tilt frames cost?
Assuming our 3kW system uses 195W panels, the extra cost of tilting 16 x 195W panels should be around $450. So to make an extra $47 per year, we are going to be spending $450. About a 9-year payback.
Whether you think this is a good investment is completely up to you. But your solar installer should give you the numbers so you can make an informed decision!
I personally wouldn’t bother, mainly because, if you use tilt frames on your roof, you can fit fewer panels on that valuable roof space.
Why?
Because you need to leave extra space between the panels so that one row of panels doesn’t cast a shadow on the row behind it. I also think that tilt frames are not so aesthetic to look at. But perhaps that is just me.
What about adding an extra panel?
The third option you have – is to make up for any lost power by simply adding an extra solar panel. A few years ago, when panels were 5 x the price, this would have been an insane suggestion (and some old school solar installers still think it is a terrible waste!) but in 2012 it can make a lot of sense.
The cost of one extra 195W panel will be about $440. Installed flush to your roof, this 17-panel system will generate 13.0kWh per day and make us $1186 per year.
So, your extra $440 investment is returning you an extra $169 per year compared to the 16-panel system mounted on tilt-frames at 41°. I’d say that the extra panel is a much better investment that the racking.
The third installer was right! (Oh! That’s us!) Call Current Generation today for common sense solar facts.
Note: One thing that you don’t want is completely flat panels (angle = 0°). You want them to slope at least 10° so that the rain flows down the slope and helps the panels self clean.
