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Sun Volt

Sun Volt Solar

earth, the final frontier

Clean Energy, Clean Environment

We are at a cross roads in human history, we can choose to continue on as we have been, or we can make a change to improve our future and quite possibly the future for several generations to come. We are here to promote energy independence, a better environment, a secure future and a higher return on investment for your hard earned dollar. It is what I believe in, it is why I am in the solar business.

Smart grid and renewable energy

05 Mar 10 | Conservation, Solar Electric

I have been reading up on the smart grid technology.  I find it interesting for several reasons.  Our energy conversion to electricity is very inefficient, around 32% for the entire electrical grid in the United States.   Because of this, we are using much more energy than we need to generate electricity.

The aims of the smart grid are:

  • Self-healing from power disturbance events
  • Enabling active participation by consumers in demand response
  • Operating resiliently against physical and cyber attack
  • Providing power quality for 21st century needs
  • Accommodating all generation and storage options
  • Enabling new products, services, and markets
  • Optimizing assets and operating efficiently

According the the US Department of Energy website.

Renewable energy critics often cite the very small percentages that renewables currently contribute to electrical generation in the US.  The other argument against installing photovoltaics is their low efficiency, between 14-16 percent in most commercially manufactured silicone modules.  Others argue that the cost is too high and the reliability is low.  All of those statements are true in the context of the artificially low prices we are paying for energy today.  If the real costs of energy were reflected in one’s electric bill, the cost per kWh would be in the $0.25 to $0.40 range.  Currently, unsubsidized photovoltaic electricity is $0.218 per kWh ($7.31 per watt installed, over 25 year life span).  Our current utility electric rates are about $0.15 per kWh.  If only the Federal income tax refund were taken (30% of the installed system cost), that brings the cost down to $0.152 per kWh.

Behind the meter solar generation is much more efficient than conventionally produced power.  A coal, oil or natural gas fired power plant dumps about half the energy consumed into the environment as waste heat.  Another 10 percent or so is consumed as resistive losses in transmission lines, then there is the energy required to produce the fuel, mining, pumping, transportation, etc.  That is what is required to use whatever fossil fuel the power plant is burning.  The amount of original energy from the sun needed to produce a unit of fossil fuel (e.g. gallon of oil, cubic foot of natural gas, ton of coal, etc)  is almost incalculable.  If we were to compare solar energy inputs, photovoltaic panels are far more efficient than any fossil fuel could ever be.

Photovoltaics also produce peak power during peak demand times, which can help reduce costs associated with Time Of Use (TOU) metering.  They are a distributed generation technology, which spreads the failure risk out over many points of generation, reducing transmission losses as well.  A battery backup couple with a solar and or wind system will keep power on indefinitely if properly sized.

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05 Mar 10 | Conservation, Solar Electric | Comment (1)

What happens to a solar system when it snows?

01 Mar 10 | Solar Electric, Solar Hot Water, solar thermal

I have good customers, they ask good questions.  One such question asked of me lately has been “what happens to my solar system when it snows?”  Since I have both a solar thermal system and a photovoltaic system on my house, I can tell them.  Enough sunlight gets through the snow that the panels begin to heat up.  This, in turn, causes the snow to slide off.  Here is a picture of a ground mounted system after receiving over two feet of snow:

Ground mounted PV array after blizzard

Ground mounted PV array after blizzard

It helps that the panels are tilted to 40 degrees, roof mounted systems likely will not shed snow like this.  Still, on a roof mounted system, the snow will melt off, it might take a little longer.  The only system I would be careful of in this climate would be an evacuated tube collector.  Because the tubes have a vacuum, no heat is transfered to the glass envelope, which is really good for collecting heat, but not so good for melting accumulated snow off the collector.

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01 Mar 10 | Solar Electric, Solar Hot Water, solar thermal | Comments (0)

WEEB Grounding devices

28 Jan 10 | Solar Electric

On our last project, a ground mounted PV system supported by a post and beam frame, I used  Unirac WEEB grounding system (UGC-1) on the Unirac rails.  WEEB stands for “Washer, Electrical Equipment Bond.”

Unirack UGC-1 WEEB ground clip between two Sanyo HIP-205N PV panels

The electrical inspector was not familiar with the product or the concept.  I showed him the spec sheet from Unirac, which details how the grounding clip creates one electrical path through the mounting rails for the ground.  Basically, the ground clip pierces the aluminum finish on the panel frame and the aluminum surface of the mounting rail.  With that electrical connection established, a ground wire is run between all of the mounting rails and connected to the grounding electrode system.  Keep in mind, that systems should have a continuous grounding path back to the service panel ground bar and cannot be bonded to the neutral or negative conductor of the PV system.

Not all electrical inspectors would accept this method and it is not currently part of the NEC, so it is better to check with them first.  Otherwise, it saves a lot of time, effort and materials to use WEEB grounds.

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28 Jan 10 | Solar Electric | Comments (0)

Prism Solar Technologies

28 Dec 09 | Solar Electric, Technology

Prism Solar Technologies is continuing to grow their manufacturing facility located in Highland, NY. They took over the PLASMACO plant last March, which coincidentally, had much of the equipment and clean rooms needed to manufacture their product. PLASMACO was a subsidiary of Panasonic corporation, they manufactured Plasma screens for TV’s and computers.

What Prism Solar makes is a proprietary holographic planar concentrator™ (HPC) film that, when used in conjunction with conventional silicon photovoltaic cells, increases the cell efficiency by about 40%. According to their website, the increased efficiency allows for use of 30-50% less silicon during the manufacture process, making the the cost around $1/watt.

Here are the advantages of HPC technology:

  • Less silicon reduces cost per watt
  • Passive tracking from holographic effect produces more energy from diffuse and reflected light.
  • Cooler operation than conventional PV module, most unusable light passes through module without being turned into heat.
  • Bifacial PV cells can increase module performance when mounted over a reflective surface.
  • Lower embodied energy, the energy required to manufacture the HPC film is much less than that required to mine and process silicon.

They have four prototype modules on line in Tucson, AZ connected to Enphase inverters. One can look at the module performance on the Enlighten website. There is also a specification sheet for a 160 watt module.

According to their latest press release, they are about to create 175 new jobs in the Hudson Valley (although there is nothing on the careers page yet). All of that is good news for the solar industry and I look foward to seeing their product out in the field. I must say, it certainly looks cool.

holographic optical photovoltaic panel

I previously wrote about them here.

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28 Dec 09 | Solar Electric, Technology | Comments (0)

System verification for Enphase Inverters

16 Dec 09 | Solar Electric, Technology

In New York State, there is something called the Standardized Interconnect Requirements (or SIR) that governs how utility companies handle grid connected renewable energy systems such as Photovoltaic and Wind energy systems.

Among the requirements, usually known as “Step 5,” a verification that the system meets UL 1741 is required. This means that after a power outage, the inverter stays off for five minutes before it begins exporting power to the grid. For most inverters, the verification procedure is simple, turn off the breaker feeding the inverter for a short period, then turn it back on. Watch the LED indicators on the inverter and time how long it takes to come on line and produce power. If it is 5 minutes or longer, the system passes.

enphase energy M210 inverters

enphase energy M210 inverters

The problem with the [e] Enphase inverters is there are many of them, they are located with the solar panels, and it would be difficult to watch the LED start flashing green especially if the inverters are under a PV panel bolted to the roof. Therefore, an alternative verification procedure must be effected. One suggestion by the utility company was to use a clamp on ammeter to measure the AC current in the branch circuit between the inverters and the panel. One small problem was that some “leakage current” had been detected in previous tests of this nature.

I sent an e-mail off the [e] Enphase Energy, Inc. They responded very quickly with the following suggested verification procedure:

  1. Turn off the breakers to the array.
  2. Turn on the breakers to the array and make a note of the time down to the second.
  3. Using a clamp on ammeter, verify that the array is not producing current until 5 minutes have passed. During the non-producing period, the ammeter will show a slight current draw of 0.056 Amps +/- 5% for each installed inverter. In this case, there are 10 inverters in each string, therefore the clamp on ammeter will show 0.56 Amps +/- 5%.
  4. After 5 minutes have passed, the ammeter will show the array producing power by indicating greater than the quiescent current noted in step 4.

The test should be run when the array is in full sunlight so the AC current meter will obviously indicate the array is exporting power to the grid since AC current meters do not indicate the direction of current flow.

The second method proscribed by Enphase involves using the utility meter. This can only be used in arrays that are large enough to get the meter spinning, and should only be performed in full sunlight.

  1. Observe service meter and note direction it is turning while consuming power.
  2. Turn off main service breaker and all other breakers feed the various household loads, simulating a power outage.
  3. Turn on main service breaker and breaker feeding the inverter(s) only and note the exact time.
  4. Observe service meter. A very slight movement forward direction indicates the inverters are consuming a small amount of power in their monitoring circuit.
  5. After five minutes have passed, the meter will begin to turn in the opposite direction, indicating the inverters are exporting power.
  6. Close the breakers to the rest of the household loads.

Finally, if the inverters are ground mounted and the LED indicators can be readily observed, this procedure can be followed if the first two do not satisfy the utility company.

  1. Turn off the breaker feeding the branch circuit, if it is not already off, then turn back on.
  2. Observe the inverter(s) status LED, is should begin to flash red when AC power is applied then flash green when the inverter(s) begin to produce power. Time the period of the flashing red LED with a stop watch, it should be 5 minutes or greater.

This can be done for each individual inverter, or for each inverter string as the (utility company) representative present desires.

According to the manufacture, the system complies with the requirements of UL1741, which states that if the inverter detects that the grid has gone out of specification or has completely shut off, then the inverter will “cease exportation” of power. The inverter is allowed to draw current but cannot produce power. Therefore the small amounts of current indicated on an AC ammeter is not leakage current, rather it is the inverter consuming a small amount of power prior to in beginning operation.

Update: From Scott at Enphase Energy:

I had a brief, follow-up comment about one portion of the article. During the 5-minute wait time specified by UL-1741, the Microinverter is not consuming power. It is circulating reactive current in the A/C-filter section of the device.

I just wanted to make sure that the statement of “the inverter consuming a small amount of power prior to in beginning operation” was not potentially misinterpreted as tare-loss, with an Enphase customer thinking that he was losing some of that hard-earned energy during the 5-minute period.

No, we wouldn’t want them to think that, especially after I preached about unshaded locations and voltage drop during the sales presentation.

I have noted that these inverters come on line in 5 minutes and 20 seconds or so after a power outage.

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16 Dec 09 | Solar Electric, Technology | Comments (0)

DIY photovoltaics

14 Dec 09 | Solar Electric

I saw this article on MSNBC:

Solar technology is going where it has never gone before: onto the shelves at retail stores where do-it-yourselfers can now plunk a panel into a shopping cart and bring it home to install.

I suppose this was inevitable.  However, before a homeowner simply plugs a solar panel into a house, a agreement is needed with the servicing utility company.  Not doing the proper paper work can result in having the electric service disconnected.  Something the article touches on briefly.

Installing one solar panel will generate about 160-175 watts of power, depending on the temperature.  This is enough to run a desktop computer, a few lights and a flat panel TV.  Obviously, if the homeowner is serious about solar electric, a larger system is needed.

One other thing the article noted:

If you want more solar power, you can snap another panel to the first, kind of like Legos.

However, each time you snap another panel on the system, the entire system needs to be re-permitted by the utility, at least in New York State.

It will be interesting to see how this idea develops.

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14 Dec 09 | Solar Electric | Comments (0)

Enphase M-190 Microverters

09 Nov 09 | Solar Electric

I had a chance to work on the installation of a Photovoltaic (PV) array using the Enphase M-190 inverters last week.  I must admit, when I first heard of the concept of Microverters, I was a bit of a skeptic.

Adding many more active parts to a system seems like an invitation for failure.  Placing those inverters outside attached to a solar panel, sometimes on a hot roof, also seems like a problem.  Finally, investing in a brand new technology from an unknown company might not be wise.

Enphase-M190-72-240-S11-MC3-2

But then I installed them.  Here is what I like:

  1. Each panel now operates at its own Maximum Power Point.  Since I have worked in electronics for over 20 years, I realize that every transistor (thus every panel) has slightly different characteristics.  Having an inverter that is able to adjust for these differences increases efficiency.
  2. Some array shading issues are mitigated.  In the Northeast there are a lot of trees.  Leave any plot of land alone for about 10 years and there will be trees growing on it.  Many home owners do not want to clear cut their property.  Using these inverters means that partial array shading will not be as devastating as it would be with a single large inverter.  Basically, each panel acts as its own mini solar array, thus if one panel is shaded, the other unshaded panels are working at full power.
  3. The warranty is for 15 years, most inverters are warranted for 5 years.
  4. The array wiring is extremely simple, it would be difficult to install these incorrectly.
  5. The array is scalable.  If a homeowner Can’t afford 100% PV power right now, install what they can afford, then revisit the situation later.
  6. May be a good solution for apartment dwellers and other renters using temporary mounting systems.
  7. Can be used in an array with different size PV modules.
  8. Monitoring service available.  Monitors and logs output of each solar module in the array, thus can track array performance and be notified of any problems.

Obviously it is better to have a shade free solar site than to compromise the efficiency of the PV panels installed.  However, this makes it a viable option for sites that have a mostly shade free solar window (9am- 3pm year round), and can live with some reduction in array output.

Regarding the issues raised in paragraph two, I think the Enphase record speaks for itself.  I would recommend these to any customer who was looking to do a scalable system, or a system using different sized or types of PV panels.  I would install these on my own house and recommend them to other people as well.  I would be very surprised if other manufactures do not come out with a miniverter product lines.

Unfortunately, the power companies around here are a little behind the curve when it comes to new or innovative technology.  One in particular has been difficult to deal with for establishing a net metering account.

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09 Nov 09 | Solar Electric | Comments (0)

PV Training

19 Sep 09 | Training

Training and proficiency is the key to installing safe, workable systems, especially where voltages of 500 VDC and greater are concerned.  Every three years the NFPA issues a new version of the National Electrical Code with updates.  These updates are based findings and recommendations from the field.  In other words, somewhere, something went wrong and caused a problem.  The incident was investigated and the NFPA incorporated fixes in the latest issue of the electrical code.  That is why it is particularly important to follow the code.

To that end, there are several advanced PV training courses available from providers like SEI, local community colleges, etc.  In order for a installer to maintain proficiency and keep abreast of changes,  reviewing the code changes as they occur is important.  Taking refresher or advanced courses is a good way to accomplish this goal as well.

In addition to this, NABCEP certification requirements have a minimum formal course requirements.

Solar energy, especially photovoltaics, is an evolving field.  The industry knows a lot more about safe solar installations than even a few years ago.  In order to maintain top notch installations, continued education is a must

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19 Sep 09 | Training | Comments (0)

Photovoltaic system details

30 Jul 09 | Solar Electric

Every installation is different, that is the number one lesson I have learned.  Those that try to get into the cookie cutter mentality often get into trouble.  This is a PV installation we are currently working on:

5 KW DC Photovoltaic array mounted on a standing seam roof.

5 KW DC Photovoltaic array mounted on a standing seam roof.

It is a 5 KW PV system attached to a standing seam roof. This system takes up about 420 square feet of roof area and consists of 24 Sharp ND-224UF1 PV panels.  We use Sunwize pre-packaged systems because it eliminates a lot of the minutiae involved in installing grid connected PV systems.  They produce well thought out systems complete with engineering drawings.  This speeds the permit process along nicely.  That being said, even Sunwize grid tied systems occasionally need some different parts than what is supplied.

First, all grid connected PV systems installed in New York state must have a lockable disconnect switch that is accessible to the utility company for safety reasons.  Because this is a pretty large house, the wire runs between the utility room and the disconnect switch are quite long.  I had to up size the wiring to stay below 2% voltage drop.  The larger wire would not work with the NEMA 3R switch provided with the pre-packaged system, so I needed to install a larger switch.

Second, this house has a backup generator with an automatic transfer switch for emergency power.  With that configuration, there could conceivably be a time when the generator is running that the inverter tries to come on line.  If the house was using less than 5,000 watts of power, the excess power from the PV array would be fed to the generator windings causing the field coils to melt.  This is a long shot because in all likely hood, the generator frequency would change dramatically when the inverter came on line causing the inverter to drop out again.  Never the less, in order to avoid any possibility of this happening, a generator running relay is installed between the inverter and the power panel.  This way if the generator is running, the inverter is forced off.

Third, because this is a standing seam roof, the traditional Unirack PV mounting racks that come with the Sunwize grid connected systems could not be used.  Instead, we used S5! standing seam mounts (S5! U mini) with PV clamps (PV anchor kit, 41-60 MM).  These worked out very well.  I used to of the S5! mini clamps to mount the combiner box at the top of the array.

S5! PV mount holding down two Sharp ND-224UF1 panels

S5! PV mount holding down two Sharp ND-224UF1 panels

We are waiting for the roofer to make an ingress port at the top of the array to make the final connection between the PV array and the inverter.  Once this is done, the system can be inspected and turned on.

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30 Jul 09 | Solar Electric | Comments (0)

Solar Green Houses

06 Dec 08 | Solar Electric, Technology, solar thermal

So what you say, all green houses use solar energy.  True enough, but where I live, in the Northeastern US, the growing season is about 6-7 months.  The rest of the year, produce is trucked in from down the Southern US or South America.

What if we could extend the growing season to 10 months?  This would really help out the farmers, who can make more money.  It would help simulate the local economy.  It would reduce the embodied energy in our food.  In all likely hood, the local fresh produce would taste better.  Remember taste?  When was the last time you had a really good hot house tomato grown 1,000 miles away.  How about that fresh local corn?  Why have we settled for bland mass produced vegetables?

There are two main problems with this scenario:

  1. In the Northeast, the cold arrives toward the end of September and does not depart until around May or so.
  2. Coincidental with the cold weather, the amount of sunlight decreases shortening the available energy for plants to convert to the produce we want.

For the first part, the greenhouses can be heated.  Conventional heating systems would waste an inordinate amount of fossil fuel, thus contributing to the problem.  Using an array of solar collectors connected to an insulated underground drainback/storage tank would work nicely.  If the system where designed correctly, it could conceivably extend the growing season into the middle to end of November.  There should be enough solar resource to start the growing season around the middle of February.   Additionally, cold weather/frost tolerant crops, such as broccoli, spinach, lettuce, cauliflower, brussel sprouts, carrots, onions, turnips, beets, et. al. could likely be grown over the winter time, as long as the soil and roots do not freeze.

Then there is the issue of light.  All plants rely on Photosynthesis to convert the sun’s energy into vegetable matter.  Through a process called “Carbon Fixation” plants take in CO2 and H2O (water), using photons (light energy from the sun), create complex sugars which are used as energy for the plants to grow.  By this process, they also release O2 (Oxygen) into the atmosphere, which we need to live and breath.   According to this chart, Plants need specific wavelengths of light to thrive:

Plants required light wavelengths

Plants required light wavelengths

Plants need specific wavelengths of light. If you shine a green light on a plant, it will shrivel up and die. They thrive, however, in the deep blue (430-460 nm) and deep red (630-665nm) regions.  To that end, LED grow lights are becoming all the rage among hydroponics growers.

Therefore, I have been working on a prototype design for a PV power LED grow light.  Something that can be used on grid with a power supply, or off grid with a Photovoltiac panel.  So far, my small panel works quite well, I am growing some spinach with it in my basement.  What is really cool, under the grow light, the plant’s leaves look black or dark gray.  That means that it is absorbing all of the light from the LED’s and not reflecting any of it back.

This light is a bunch of 5mm LEDs wired in series.  It is designed to work on a 12 volt system.  It covers about 1 square foot of growing area and uses 12 watts of power.  It cost $125.00 to prototype (or $1.15 per square inch), although production costs would come down considerably if it were mass produced.

I am currently working on a high powered design that will cover 5-6 square feet of growing area.  It will use 88 watts of power and cost $398.00 to prototype, or about $0.49 per square inch.   Again, costs would come down considerably on a production run.

Larger arrays of these lights would cost even less per square inch as economies of scale takes effect.

There are some advantages to LED’s over conventional grow lights:

  1. LED’s are much more efficient, producing less heat (thus less wasted energy) than conventional grow lights.
  2. Long life.  My prototype LED lights are rated for >90,000 hours.  Using a LED grow light for 12-16 hours per day, that translates to 17 years.  If they are used for supplemental growth (e.g. 8 hours per day for half the year) then the life span would be about 60 years.
  3. It is generally though that LED’s are about 4 times as efficient as High Pressure Sodium (HPS) lights, so a 90-100 watt LED light could replace a 400 watt HPS light.
  4. Light can be tailored to plants or desired outcomes.  Most experiments show adding more blue light (430-450nm) increases vegetative growth.  Adding more red light increase flowering. Other wavelengths can be added depending on the plants needs.

The question is this; will this technology become economical in the future for ordinary growers to use?  Growing food locally would certainly cut down on the transportation costs and the associated polution of long distance farming.

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06 Dec 08 | Solar Electric, Technology, solar thermal | Comments (3)