Green Spark Solar Blog

Solar Power

The Accuracy of the EECA Energywise Solar Calculator is Questionable

In late 2016, the New Zealand Energy Efficiency and Conservation Authority (EECA) produced and marketed a solar calculator, claimed by them to assist homeowners in making decisions about solar power.

The calculator was heavily promoted and advertised, both on TV, Facebook, Google Adwords and print media.

Unfortunately there are some strange inacuracies built into this device – it gives misleading results, and according to the NZ Green Party, it attracted a deluge of complaints as soon as it was launched.

Many of these complaints and criticisms ended up in a steady stream on the Facebook page for EECA Energywise. Just as steadily, EECA mysteriously deleted these comments.

In terms of power production in kW per annum it is actually reasonably accurate. The calculator relies on NIWA data and it matches what solar installers know about their customer results. From that point there is a major divergence.

The basic problem is that the calculator acknowledges zero storage during the day, when in fact almost all Kiwis already have plenty of storage, in the form of hot water tanks, underfloor heating, night stores, spa pools, swimming pools and deep freezers. All of these devices can be run on timer systems so that they activate during the day using free solar energy, and turn off at night. Washing machines and dishwashers can be used selectively for day time only use for a similar results.

Using LED lights with solar is as common as icing on cakes to reduce night time lighting costs, also noticeable by its absence.

When I asked the calculator’s inventor, Dr. Alan Wood why these important factors were not included in the calculator. He said “It is true that energy storage and customer behavioural change are not modelled….it is extremely difficult to include the effect of these extra behaviours”.

I asked him if he would agree that any calculator not including storage would give a vastly distorted result 10 years or more out of sync with reality – I never got a reply.

I ran a quick scenario with an average power bill and the calculator gave me a result of about 18 years to break even, a result I believe to be nonsense because of the number of customers with the same bill we personally know that get a much superior outcome. My colleagues and I repeatedly asked EECA to provide examples of real people that are getting results matching their calculator. Not only did they never reply, but they deleted our persistent questions from their Facebook page.

There are some other assumptions within the calculator that look a bit dubious. One of these is the predicted future price of power being at 1.5% (about the same as the CPI). However, historically power has been increasing in price at a much higher rate – about 5.85% from 2003-2012 according to the MBIE. Future demand for electricity is also likely to be heavily influenced by the rise of electrical vehicles. All the energy coming directly from petrol and diesel will have to be supplied by electrical generation. This is not acknowledged in the above estimates.

With the cost of power rising rapidly, the relative savings of a solar system also increase rapidly. In fact, the relative savings increase at a faster rate than any degradation

The calculator also assumes that a solar system lasts for 25 years. Dr. Wood is confusing warranty periods with system life. So at 25 years, the system will still be operating at 80% efficiency and extra panels could be added at that stage to bring it up to a higher level, it is only the warranty that would expire. Because the level of panel degradation (0.5% on Duomax panels) is less than the rate of power price increases, in 25 years it will actually be saving more money than in year 1, not less.

There is a Net Present Value NPV section included in the calculator that compares the return on investment compared to another investment (money left in the bank). There are several problems with this approach:

-         It doesn’t acknowledge that a solar pv system adds value to a house as soon as it is put on. A solar powered house is easier to sell and commands a higher price.

-         Whatever savings are generated from the solar system are tax free. But bank account earnings are taxed.

-         Solar systems have warranties covering their output performance (effectively a guarantee, which banks do not have).

-         Solar savings are normally left to accumulate in a bank account, generating compound interest over time. For most clients, this ends up being about 10 times the financial benefit if they had left the money in the bank instead of investing in solar.

-         The choice is not between paying for solar or having no power cost at all. This is because if a client didn’t have solar they would still have to pay for power from the grid (at a higher rate). Either way, the money gets spent anyway – the real choice if a client wants an investment or not. It’s a bit like the difference between mortgage (ownership) and rent.


So why is EECA doing this? Dr. Wood says that he is receiving no financial advantage at all and I have no reason to disbelieve him. But you look at the bottom of the calculator in the disclaimer section it mentions that  Transpower is partially funding his research program.

Transpower owns and operates the nationwide grid in New Zealand. In some circles it is thought that solar power presents a great challenge to the viability of the national grid, because as more people use solar the less they need Transpower’s services and the less economic these services become.  On its own website it states that

“Transpower has a major investment programme to address:

-         Strong recent growth in electricity demand and predicted growth over the next 40 years.

-         The need to connect a diverse range of new sources of generation.

-         The ageing of the grid”

March 26th 2017

Energy Disaster in South Australia opens golden opportunity.

South Australia’s energy grid has taken a battering recently. Firstly there were   a series of terrific storms over a few months, with enough force to physically blow down several pylons. Then there was a period lasting more than a month with soaring temperatures more than 40 degrees every day. Black outs ensued - the grid was not able to cope and millions of people got roasted in the dark.

Part of the problem is the privatisation of the power industry in Australia - essentially if it had been centralised then other backups could have been implemented quickly.

South Australia did away with coal fired plants forever in 2016, with a large portion of is generation being taken up by wind (43%) and solar. Unfairly, these technologies were blamed for the outage, when in fact it was largely a physical problem with the lines themselves (they fell over).

Elon Musk came up with an audacious plan to deliver 100-300 Megawatts of centralised battery storage, to be installed in 100 days. Sounds crazy, but no worse than building your own rockets to Mars. History suggests he can probably pull it off. This would be a new thing,to install  a battery bank large enough to stabilise a whole state and it could shake up global expectations of what is practical and achievable in this area.

Centralised battery storage is the most obvious way for power utilities around the world to stay relevant as the solar revolution gathers pace. As I wrote in an earlier post,  tiny Alpine Energy in Timaru actually already does this on a more modest scale. Daytime generation is stored in a room sized Lithium battery and released at peak evening times.

It looks like the SA state government is going to go ahead with Musk or another battery provider, but rather than take the bold step of using more and newer solar systems to provide power generation, they decided to implement a yesteryear gas fired plant. It’s a bit like going back to using analog phones or black and white television; but the power instability is doing wonders for the domestic solar industry over there, where ordinary citizens can own their own power plant and battery bank and be fully independent if there are future blackouts.

March 19th 2017

Why Lead Nanocarbon Batteries Beat Lithium.

In many ways it seems Lead Nanocarbon is Lithium’s ugly but smarter sister. Lithium is in the media a lot, it’s the sexy technology behind the Tesla Powerwall and electric vehicles. It’s associated with Elon Musk, the leading entrepreneur of Silicon Valley and larger than life personality behind Iron Man.

Lithium has many advantages - a fast charge/discharge rate and a lighter weight (hence its use in electric vehicles), nothing competes with it in terms of energy storage per kg. But for home use, the weight is meaningless.

Lead Nanocarbon, Pb-C or Lead Carbon you hardly ever hear about. Manufacturers like boring Narada spend nothing on wooing the media. The heavyness of the lead makes it unsuitable for vehicles. Just one 6V battery weighs 60kog. Yet for domestic situations it is Numero Uno

It is difficult to compare apples for apples in this area, probably that is deliberate because warranty terms on Lithium batteries don’t hold up to scrutiny very well; I will take arguably the most popular battery on the market today, the LG Chem Resu 6.4 and break down the warranty into bite size chunks.

It says in the sales literature 6000 cycles at 90% DOD which sounds impressive but when you look at the warranty, you see they only allow for 16.1 mWh of capacity.

6.5KW x 90% = 5.85 x 6000 cycles = 35,100 mWh . There is a disconnect between this and what you are actually covered for - the boast is double the reality. If you do the calculations it is really 3,100 cycles at 80% DOD. LG is counting on people being too lazy to count and being pretty successful  by the look of things.

In terms of price, an LG 6.4 is about the same as 14.4KW of Nanocarbons. So in pure KW terms you get more than double the storage for the same price.  To work out bang for buck, lets compare the two at both 80% and 50% DOD for their warranties as these are the most common levels :

14.4KW X 80% DOD = 11.52KW X 2400 cycles = 27 mWh for Nanocarbons vs. 16.1 mWh for LG.

14.4KW x 50% DOD = 7.2KW X 3600 cycles = 25.9 mWh for Nanocarbons vs.  16.1 mWh for LG

Nanocarbons thus are ahead by a long way in terms of value and capacity.

In addition, they are safer for home use as Lithium can be explosive if it becomes overheated eg. a house fire. Also, Nanocarbons work over a much wider temperature range; and their charge/discharge rate is much higher.

Lastly you get degradation with Lithium over time, whether you use them or not, while Nanocarbons only degrade if they are fully charged and not being used. It is possible to get a good 14 years of service out of the Nanocarbons, if you are discharging only down to 50% DOD, while there is no Lithium battery out there than can do that.

February 20th 2017

Lithium Ion batteries vs Lead Acid

There are a few tools to compare solar batteries and what they do, their cost effectiveness and efficiency in the real word. There is also a lot of deceptive statistics and a few bogus warranties around.

The most common measurement is DOD (Depth of Discharge). Don’t confuse this with SOC (State of Charge) because it is its opposite. DOD is how much you can use, SOC is how much you have left. Traditional lead acid batteries can be run safely down to 50% DOD, while Lithium Ion can go to 80%. DOD is measured in Kilowatt hours (Volts x Amps/hr) - basically it means the number of kW you can use before it conks out.

So to achieve a similar result in terms of DOD, Lead Acid needs to be 30% larger than Lithium in kW. Another rule of thumb is double the amount of Amp hours.

As far as price goes, for the same amount of Amp hours, Lithium is about 3.5 times more expensive.

For weight, generally not relevant for home use, but highly relevant for electric vehicles, lead acid are about 4 x heavier for the same kW.

Most Ah ratings are calculated at the 20 hour rate. For lead acid, the higher  the load, the more volts required and the lower the level of useable energy. The higher the load then more you need to increase Ahr capacity. But for Lithium this isn’t the case - a load 10 times greater will still have the same volts. So Lithium is much better for higher loads, and the longer this load is on, the more exaggerated the difference between the two chemistries.

Charge rates are important - lead acid can only charge normally up to about 60% SOC before it starts hitting resistance - it gets harder and harder to charge it up to 100%. Higher rate charging does not make it charge any faster. However with Lithium the charge rate is fairly stable up until around 98%. Therefore in both charge and discharge, Lithium is ahead.

For cycle life, there are many different measurements of cycles at various levels of DOD, but if you.consider full charge/ full discharge, then lead acid will give you 400-1500 cycles while Lithium gives 2000-4000. So for longevity, Lithium gives you between 2.5 and 5 times more cycles depending on how the battery is used. Other factors to consider are the time and cost involved with replacement as well as the less efficient use of power to charge lead acid up in the first place and whatever costs that might incur.

There are some other issues around safety - lead acid gives off hydrogen, an explosive gas as well as liquid sulphuric acid that can splash into your eyes and slosh all over the place (but not if you have sealed lead acid or AGM type). Lithium has safeguards built into the battery, but if there was a general fire near the battery there is a possibility it could heat up and explode.  On the balance on safety they are probably about equal.

Lead acid can be taken away and recycled. Lithium batteries can be removed and replaced easier due to their light weight, but at this stage there are not general recycling facilities, at least not near Christchurch, New Zealand.

It might come down to this - first see if you are going to have heavy loads like heating, washing machines, microwaves etc. then see if you prefer to have something really modern with a longer life for a higher price or something cheaper now but maybe more expensive over the longer term.

February 18th 2017

Wind vs. Mircohydro vs. Solar for domestic use.

These three systems are all ways that a house can generate its own power using technology available today. These solutions tend to be site specific to a greater or lesser degree, I will explain their various strengths and weaknesses and give a comparison.

Wind for domestic use generally doesn’t work too well inside cities or towns on flat ground, because of the obstructions to wind from buildings and trees. In a rural, exposed area with relatively constant wind it can work well. Wind power works day and night and in overcast conditions but on a calm day it will produce nothing. Domestic considerations are on the noise production and allowable height of the wind tower.  So for example, a 400W turbine is often enough to cover the draw of an empty house during the day when no one is home and it is windy. This is a four foot diameter rotor on a tower 12 foot tall, roughly as high as a house. It will probably make enough noise to annoy the neighbours if they live next door.

For a large house on a lifestyle block or farm that wants to be fully off grid, they would probably need a 10KW system on a 23 foot turbine on a tower 100 feet tall, together with battery banks and diesel generator or solar back back up. Wind power does require 6 monthly extensive maintenance because it uses moving parts with constant wear and tear. There are safety features inside most turbines to prevent them spinning too fast in very strong winds.

Microhydro is the most site specific and in the right conditions the most constant power producer of the three. It can only be done if there is a stream or river in the backyard. There must be a 40 metre vertrical drop in the flow of the water and the rate of flow must be at least 12 metres per second. In most cases a dam is not required, but if it is then specific resource consent is also a necessity. As long as the water flows in the stream then the power output is constant. Mini generators can be built up in series to give a large amount of power, with a much lesser need for battery storage. The installation can take a long time, sometimes weeks. For return on investment, micro hydro is thought to be at least 10 times as good as wind or solar; however anecdotally there are a few reports of the the whole system being swept away in the first flash flood. Like wind, there will always be a need for ongoing maintenance.

Solar is the least site specific of the three, but clients still need to have a N or E/W roof with minimal shading and enough roof space to take the panels. It is silent and essentially maintenance free because there are no moving parts whatsoever. Unfortunately it does not work at night, but there are many ways to store energy during the day for night time use beyond batteries - namely hot water tanks, also pools, spas, underfloor heating and night store heaters run in reverse.  That is equally true for other forms of energy production. 2 solar panels have about the same output as one domestic wind generator, but an average 3kw system will have 12 panels, so for bang for buck and practicality of installation it beats wind hands down.

At this stage it seems solar is the most popular and viable domestic electrical production system, but there is no reason why they can’t be combined together when the site conditions permit it. Solar does complement the other two because when there is a drought the sun is shining and overcast days also tend to be windy days. I have even systems where solar cells are buil into the turbine blades.

December 10th 2016

France makes solar power mandatory in all new builds - not.

Pollution levels in Paris have been getting dangerously toxic in recent times. Paris has been forced to use an alternating odd/even car number plate system to reduce road traffic and alleviate emissions.

In keeping with this theme, France has made solar power installations or green roofs mandatory in all new domestic and commercial buildings across the country. At least that is what we were told on the blogosphere. Unfortunately it got blocked by the right wing Senate with construction companies threatening to pass all installation costs straight on to consumers and the conventional power sector doing it best to stifle the rapid growth of PV, as it has done in other countries too.

However, Toronto, Tokyo, London, Copenhagen and several large cities in the US have had successful green roof/ PV incentive programs since around 2009. Perhaps incentives like tax breaks, fair feed in tarrifs and a sharing of installation costs are a better way of improving society than legislative mandates.

Green roofs combine easily with solar power, the cooling effect from the greenery improving the performance of the panels and the shade from the panels providing protection for plants.

Even with this setback, France is still the seventh largest producer of PV electricity in the world at an estimated 6 GW and it is continuing to grow.

December 7th 2016

Spinning solar panel cone most likely a scam

Lately on social media there has been claims made by V3 Solar that they have developed a solar cell system that delivers 20 x greater power production of regular flat silicon based panels.

The idea is that the cone shaped solar cells are set to spin under a glass solar concentrator. The glass lenses focus the sun’s energy and the spinning effect cools the solar cells allowing them to perform at peak efficiency.

Sounds good, except it is probably nonsense.

Encasing panels in a glass structure will heat them up due to the greenhouse effect, even with ventilation holes. A circular structure will have reduced surface area to the sun and the spin doesn’t seem to have any kind of fan or obvious cooling function. Anything that moves will require more energy which has to come from somewhere.

Keeping solar panels cool is sound science because heat does cause a loss of efficiency. An easier way to do this is to mount them on floats above water sources like lakes and reservoirs.

V3 used to be known as Solarphasec who also had a cone shaped solar panel a few years ago. The idea has been around since 2013 but we haven’t seen any examples come to market yet. They have spent a lot on marketing and are clearly interested in attracting gullible investors.

December 5th 2016

Tidal Power in New Zealand

Tidal power has a lot of things going for it - it is renewable and reliable as a clock but it hasn’t been exploited much in NZ due to uncertainties about the future structure of the power industry here.

In 2011, resource consents were successfully obtained for a tidal power station in Kaipara harbour. This would consist of 200 underwater turbines with enough generation to power 250,000 homes but it got put on hold because of the chaotic effects of privatisation on the power industry and the possibility of a future Labour/Green government centralising (meaning organising) power once more.

There are several forms of tidal power. In Kaipara, the turbines were planned to be 30 metres deep in a channel where the tidal flows are particularly strong. This type of system ( termed Tidal Stream Generation) does not interfere with the action of water and sediment appreciably but there may be some issues with marine life getting caught in the blades of the turbines or avoiding the area due to Electro Magnetic Forces EMF, or underwater noise. The proposal did however pass an assessment by the Environment Court

There are other forms of tidal power that can supply storage that integrates with solar or wind energy with less of an environmental impact. One such is the artificial Tidal Lagoon. This is circular walled structure with a turbine built in a place where it does not interfere with the local ecosystem. Extra seawater can be pumped into the enclosure during times of peak solar or wind production, and the water released on demand as long as the tide is at a generally lower level than the water inside.

At least two other locations in the Cook Straight and also the Chatham Islands already have consents and are just waiting for the right political environment.

December 1st 2016

German Adventures in Solar Power

Germany is the second highest PV installer in the world at 40,490 Megawatts, only surpassed by China. There are approximately 1.4 million solar systems installed across Germany. This is despite the weather, with a large number of overcast days and large seasonal variations in production, particularly in the north of the country.

Much of this success is simply due to government policy. In 2000, the Renewable Energy Sources act was implemented with high tariffs guaranteed at around 60c per kWh. This was in line with the renewable energy target of 60% by 2035.

The cost of these tariffs was distributed across all consumers, but interestingly the cost of grid power actually declined during this period, with savings of up to 40% during peak output times.

As in NZ, the utilities panicked, and instead of adapting to change by supplying centralised energy storage, they put pressure on the government to reduce the tariffs, so that today they are around 12c. The boom period in Germany was during 2010-2013 when around 7 GW per year was installed, representing about 30% of world wide PV installations.

Since that time, solar is still growing but at a much slower rate. It is estimated that about 50% of jobs in the solar industry in Germany were lost. Both brown and black coal are still being burnt and nuclear stations are still running, though the latter are expected to cease in 2022.

Meanwhile solar power keeps declining in price and becoming more efficient. Batteries only have to come down a little bit and there is likely to be another resurgence, even if there is no tariff at all.

November 30th 2016

India’s Ambitious Solar Power Plans.

India was a relatively late player in the current solar revolution, mostly relying on coal and nuclear until 2010.

Since then there has been a literal explosion of solar activity, with 8.63 GW installed as of 2016. That in itself is pretty impressive. Like so much of green technology, the main driver has been economics. India has to import much of its coal and solar energy is simply cheaper. By 2022 the Indian government has projected 100GW of solar capacity. This is more than Germany and China combined.

Most of this solar installation frenzy will be installed to keep pace with the growing population and to deliver electricity to rural areas, about 50% of which have no reliable access to power. The nuclear and coal plants will keep chugging on though because of the high cost of totally replacing them, but the economics will likely catch up with this too.

The domestic solar manufacturing industry is relatively minor compared to China at this stage and is expected to grow significantly with the massive demand. Some of the challenges of installing solar in India is the lack of enough roof space and spare land. Possible solutions are to have the panels floating on special rafts on dams, lakes and canals as this space is free and loss of water from evaporation is another issue. Another possibility is to mount them high above roads, their shading giving greater comfort to drivers and reducing the heating of cities generally.

 India is famous for severe air and noise pollution of all kinds and the effect of solar combined with electric vehicles will be dramatic

November 27th 2016