Dennis Houghton's Comments

49 minutes ago

Proof in Numbers: Putting Solar Job Census & Home Value Study in Perspective

Another report on this website described the employment mix for the solar PV industry in the US. Approximately 175,000 FTE total with @95,000 installation, @ 23,000 manufacturing, some R&D, marketing and other non-installation jobs. These positive results show about as many PV installers as blue collar coal miners, both above and underground, in the US job market. An interesting inflection point.

Another report analyzed average installation costs by component and revealed an "unsustainable" cost of sales at $0.48/Watt. Efficiency in the PV market will require drastic reduction in cost of sales, especially when the tax credits expire.

New microinverter and racking systems will make the installations more homeowner friendly and further reduce installer job growth numbers.

The industry will continue to grow impressively but job growth can not track that project growth for much longer

January 03, 2015

When an Inverter Manufacturer Goes Bankrupt: Facing the Impact from Different Angles

Mr Donovan,
Enphase is one microinverter manufacturer which uses proprietary interconnecting cables which are probably not plug and play interchangeable with another brand. In addition the microinverter connects to an AC combiner device and then feeds a 20A CB in a panel. It does not connect directly to a residential outlet.
A 25 year warranty on microinverters compared to 15 years for central inverters is an actuarial artifact rather than a definitive quality indicator. Warranties are corporate bets that future costs will happen long after current profits are absorbed. Corporate bets are often incorrect.

January 07, 2015

When an Inverter Manufacturer Goes Bankrupt: Facing the Impact from Different Angles

Brian, I was unaware of the direct plug-in PV systems and would like to know more.
Please suggest a brand that employs direct AC plug connection to a residential electrical system.
I do not consider warranties beyond the 15 year NEMA standard to be any more than a marketing technique.
The industry will mature into some form of an installation/service model that will maintain and renew system components at reduced future costs.
You are correct about concern about capacitors. In the 1970s the NEMA standard for voltage withstand rating of capacitors within HVAC equipment was reduced by about 20%. The modern HVAC service model was born.
A large number (maybe 50%) of residential HVAC service calls involve capacitor replacement. It is easy to diagnose, cheap to replace and provides the opportunity to upsell.
While PV cells/modules and PV inverters are both semiconductor devices. Solid state with no moving parts larger than electrons. The difference in expected /warranted life span is due to how those electrons are managed.. In the PV material, huge numbers of photons impart energy to an equal number of electrons. Each interaction involves an infinitesimally small quantity of energy which is collected to provide an output voltage and current. The inverter receives all this energy and delivers it in timed pulses to the AC output. Inverter outputs are typically high speed switches such as IGBTs which will operate at full power hundreds of times per second. In addition, every pulse of the inverter output produces a reflected voltage up to 3 times higher than the nominal output voltage. It performs these high energy switching actions up to two trillion times per year

December 15, 2014

Can Solar Companies Really Be Called ‘High-tech’?

Mr Coomber, when I search for " stage [4] Solar PV technology products " as noted in your comment, I have only found one document reference. A U of C Berkeley market analysis with five stages of technical product development. Stage (4) is Diffusion and Commercialization. I think you are referencing a different analysis, I would appreciate a link. Thanks

November 15, 2014

Calling All US Solar Warriors: We Need to Stand Up for the Industry

Mr Kodzis
When you mention residential demand charges are you referring to the system where users are charged more per kilowatt-hour after a certain consumption level is met. It would be measured by a separate demand meter which looks for peak consumption for 15 minute intervals. The highest consumption in any 15 minute period sets the demand price for electrical service above the demand limit, for the entire month. Residential users will object vigorously. They will also recognize that efficient use and timer controls provide a better ROI than PV in this circumstance.
Perhaps you are suggesting a reverse demand charge where you pay more if you use less than the utility has specified. This would punish PV owners and reward utilities, which would be the motivation to establish such demand penalties. Those who do not own PV systems sometimes use the argument that PV owners are not paying their full share of utility infrastructure costs.
Demand charges are common with large industrial and commercial users where the infrastructure serves only a few facilities. These businesses spend a lot of money on efficient operations to avoid these charges, often reducing production for multi-hour periods. The charges can amount to thousands of dollars a month and can be triggered by a simple controller-operator error. Residential users will object to an identifiable charge on their bill because they had their clothes dryer, hot tub, plasma TV and heat pump on at the same time.
Most utilities already have a residential monthly minimum bill which ostensibly covers infrastructure costs

November 17, 2014

Calling All US Solar Warriors: We Need to Stand Up for the Industry

My daughter and her husband recently had a 10 kWp PV system installed on their home in Kiel, Germany. The cost was < US$2.50/Watt nominal. About half of the cost of the same system in the US. Homeowners can manage permitting, inspection and FIT registration online. Designs can be selected from a pre-approved set of block diagrams. Contractors are installers in overalls, not project developers, permit specialists, site analysts and certified designers. Most skilled electricians can assemble the components of a PV system and most of them also understand azimuth and elevation. Some systems require real engineering, most do not.

The "Solar Warriors" clinging to the ITC model should recognize that all that white collar overhead is only sustainable with very expensive products, like nuclear power plants and residential PV, 15 years ago. The German FIT model has many flaws but has succeeded in lowering the total cost of ownership and encouraged widespread adoption of residential PV.

The value added by the non-productive part of the US PV business model surely can not equal the total cost of physical installation in Germany, can it???

July 17, 2014

3 Noteworthy Solar Implications in New US National Electrical Code

Mr Collins,
You are correct that properly installed solar PV is not a significant fire hazard in itself. The NFPA publishes many other code books dealing with manufacturing and installation of combustion appliances and systems. The NEC requirements mentioned are a resolution of firefighter life safety issues.
Visualize the home in the picture with an attic fire caused by a faulty gas furnace chimney right under the middle of the PV array. The north side is not part of the attic so firefighters must ventilate the attic through the array. The firefighter will use his axe with an insulated handle to smash several modules out of the way. Each axe blow leaves exposed live parts at the array voltage. The DC side of the system does not shut down through overcurrent or short circuit protection but perhaps only through ground fault protection. Otherwise the module conductors will stay energized posing a life safety issue to firefighters.
DC circuits can readily sustain arcing at low voltages, i.e. DC welding, raising the possibility of causing additional fires on the roof. Fires not caused by the PV system but by damage to the PV system. The changes to the 2014 NEC do not fix this problem at the module level but will standardize the local requirements for fire department rapid shutdown.
As for setbacks from roof edges. I am sure a couple of young guys in shorts and sneakers had no problem installing those modules but then they did not have to deal with smoke, flames and spraying water while they worked.

July 26, 2014

3 Noteworthy Solar Implications in New US National Electrical Code

In an introductory PV segment for apprentice electricians we demonstrate how a broken PV module can have live voltages even when broken into three pieces. We have two identical modules except one has been broken. We lay them out on a table under florescent lights and usually reach nameplate voltage on the undamaged module. We isolated conductors along the broken edges and measured voltages that were a major fraction of the module nameplate voltage. The sum of the voltages from the pieces was less than the module nameplate and could be treated as low voltage presenting minimal hazard. The series-parallel connections of multiple modules develop higher and more hazardous voltages.
Nameplate voltages are present even when the module is disconnected from the array. Take it out of the box, expose it to light and it is an energized component. Break it into pieces and the pieces are still energized.

Mr McCune, your comment "amazing that an electrical product was manufactured for decades without an off switch" made me wonder if you are developing and isolation product for small storage battery systems. As storage becomes part of more PV systems the disconnection of the series-parallel connections of battery racks will be a major issue. The available fault current from even a small battery system will pose a much greater fire and life safety hazard than a PV array

June 27, 2014

Sir Richard Branson: “We’re Killing the World”

There are about 5000 jet airliners aloft at any given time, 24/7. Each of those aircraft consumes about one pound of kerosene/jet fuel per second. Every day we intentionally inject more than a million TONS of high temperature CO2 and H2O, high in the atmosphere. Gosh, I hope my math is wrong.
5000 aircraft X 24 hours X 3600 seconds X ( 1#/second) = 432 million pounds or 216,000 tons of jet fuel burned per day. Jet fuel is basically C12 H24 and combusts into 12 CO2 and 12 H2O molecules for each molecule of perfectly combusted kerosene. One ton of jet fuel becomes many tons of CO2 / H2O. Plus some NOx and SOx and particulates for flavor. Once again, all this energetic jet engine exhaust is injected into the atmosphere at 35,000+ feet. If something is invisible, does it actually exist?
Sir Richard knows this very well. He also knows that his businesses are major contributors to the high altitude pollution problems, largely ignored by almost everyone.

June 28, 2014

Sir Richard Branson: “We’re Killing the World”

There were no suggestions in my comment, only observations about high altitude emissions which are an insufficiently studied source of greenhouse gases.

I agree completely that humans will continue dig up and burn carbon until it is gone or it kills us.

July 01, 2014

Sir Richard Branson: “We’re Killing the World”

Mr Gelbert, I am actually more optimistic than my previous curmudgeon(ish) response might indicate.

Tomorrow, NASA plans to launch OCO-2, an orbiting carbon observatory. Soon we will have real data about the atmospheric column mapped by location.
We already have precise information about the airline routes so correlation should be easy if it exists at all.

Stay tuned.

Dennis Houghton

Dennis Houghton

Electrician instructor, Instrument technician, Electrical code inspector, Grid tied solar PV trainer, VFD application trainer

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