20140209

Is it safe to come back?

Sorry for the neglect here. Hopefully the circus has left town and I can get back to my normal topics. I’ve also cleared my backlog of comments awaiting approval, most of which were SPAM. Since I cleaned out my flickr account, the images in several of my older posts have disappeared. I’ll clean those up as I have time.

20120114

Technology Gateway Video

First the disclaimers: While I do work for NASA, I do not speak for them.  They employ me for my professional capabilities and on occasion my professional opinion. Nothing I say should ever be construed as anything other than my personal opinion. As a NASA employee I am allowed and often times encouraged to say what I think. This and the exceptional people I get to work with every day are what make NASA great and a great place to work.

I wish to respond to a number of things that have popped up on the web in the past few days and weeks. I do this here because I can control the message. Every issue has at least two sides but, only the writer gets to decide how to present them. I do not plan to make discussion of my work on this site a habit and I do not plan to allow any comments to this post. It is unlikely that any email on this topic sent to me will generate a reply. Undoubtedly, bits and pieces of this will be taken out of context and used to support claims and opinions which I myself do not hold.  Such is the nature of the Wild West Web (WWW).   All I can ever hope to do is to maintain the original content and context.  In my opinion, reputable sites will link back to this original content and others will not.

As you have likely already noted, a non-technical video on a patent application for a new technology was made public on a NASA website this past week. It is part of the overall innovation disclosure process.  It is just one of the ways NASA communicates with the public about what we do. As mandated by Executive Order, every civil servant is required to disclose an innovation or invention which may be a of value/benefit.  Google “NASA technology reporting” if you wish to read the executive order and how NASA has implemented it. If a patent application is filed, a video may be produced to inform the general public of the nature of the invention or innovation.  It may be a non-technical piece that communicates what this invention is about and why people might care.  Such is the case of the recent video on Surface Plasmon Polaritons.

As for what people are trying to read into this video, specifically my use of the word “demonstrated”, it is my professional opinion that the production of excess energy has been demonstrated when the results of the last 20+ years of experimentation are evaluated. There has been a lot of work done in the past 20+ years. When considered in aggregate I believe excess power has been demonstrated. I did not say, reliable, useful, commercially viable, or controllable.  If any of those other terms were applicable I would have used them instead. If anything, it is the lack of a single clear demonstration of reliable, useful, and controllable production of excess power that has held LENR research back. As a non-technical piece aimed at the general public, my limited media training has taught me that less information/detail is generally better than more. I did not produce or direct the video. While I saw the video before it was released, I did not learn of it’s release until the email started pouring in Thursday morning.

There have been many attempts to twist the release of this video into NASA’s support for LENR or as proof that Rossi’s e-cat really works. Many extraordinary claims have been made in 2010. In my scientific opinion, extraordinary claims require extraordinary evidence. I find a distinct absence of the latter. So let me be very clear here. While I personally find sufficient demonstration that LENR effects warrant further investigation, I remain skeptical. Furthermore, I am unaware of any clear and convincing demonstrations of any viable commercial device producing useful amounts of net energy.

So what does extraordinary evidence look like? As a trained scientist, I have been taught the historical standards for acceptance of experimental results or theories. Experiments and theories go hand-in-hand in what is known as the scientific method.  Both must be independently tested, replicated, or verified.  As a minimum, experimental results must be replicated by an objective and independent party. The nature of the test or replication needs to adhere to the spirit of the original experiment but, should be under the full design, implementation, and control of the independent tester. So, if a device is claimed to be capable of producing excess heat by nature of its operation (i.e., the consumption of fuel via a nuclear process), it must be operated properly. The way power input and power output are measured should be left up to the independent tester. This is standard scientific practice. What would take this to the next level (extraordinary evidence) would be to have the test be an open public test. The nature of the test and specific approach to executing the test should be made public. The conduct of the test should be open to additional 3rd party experts. And finally, the data should be publicly released. Further peer review of all aspects of the independent test is a must. Community consensus is the ultimate goal. Every attempted demonstration of a LENR device that I am aware of has failed to meet one or more of these criteria.

There is one last point I wish to cover. It has been claimed that I no longer give proper credit to Widom and Larsen for their theory. I disagree with that opinion. When I talk to my family, friends, or neighbors about some of my work. I do not cite Widom-Larsen Theory or any of their papers. There would be little point in doing so. Who the intended audience is must determine what you say and how you present the information. If a technically competent person comes across a non-technical presentation they should recognize it as such.  To expect that every form of communication is exactly what you need or want it to be is unrealistic.  The fact that Widom-Larsen Theory (WLT) was not explicitly mentioned in the video fit the intended audience. It is not an indication that I no longer believe WLT is likely the correct explanation behind LENR. I have been consistent in my professional briefings to indicate that I find WLT is likely correct. It appears in every briefing where I have had the time to include it and where the briefing was intended to be technical. I’ll point to my last public technical briefing at NASA GRC as evidence of this. I will continue to do so until such time that WLT has been demonstrated to be flawed. Quite frankly I am baffled that WLT is not receiving more wide spread attention. Applications of the theory appear to go far beyond LENR. The fact that I did not mention WLT in the Aviation Week article was a mistake on my part. It was a technical article to a technical audience. I communicated my regrets on that omission directly to Lewis Larsen and am quite willing to admit that error publicly – mea culpa.

20110306

Not a good day at the launch site

The day started out pretty well. I had a car load of untested rockets and Ol’ Faithful, my BDR 4.0 that I used for L1, & L2 certifications as well as my first dual deployment. Our club has a couple of contests going, a 2000′ and 9000′ challenge.  I started the day with the maiden flight of my Aerotech Cheetah on an F52T-8 motor.  It flew well to 2018′.  I wish I had entered it into the 2000′ challenge.  Next I flew the Lil’ Rascal on its maiden flight with a CTI H400 Vmax motor.  Woah, Zero to giddy-up in a blink. The rocket suffered a severe case of road rash by being dragged across the broken concrete of a WWII era runway by its parachute.  The crowd loved the flight!  I then flew yet another maiden flight with my stretch Vulcanite.  This one I did enter into the 2000′ contest with an H90 motor.  It only went 1811′ – much lower than the 2025′ in the sim (the Cheetah simmed out at 2022′).  It was an exciting flight because the electronics bay pulled out of the upper tube but did not deploy the main parachute.  Being a dual deploy rocket, it looked like it was going to be smashed to bits.  Fortunately, it hit very wet grass and suffered absolutely no damage.  Now it was time to break out Ol’ Faithful.  I had built and installed a keychain video camera in an external pod on the sustainer.  I prepped the rocket and took it out to the launch pad.  I forgot one crucial thing and this is what happened.  The electronics bay and payload section survived.  All else was a total loss.

20110104

A Goal for 2011

Accomplishing one of my goals (dual deployment) on the very first day of the year has me in search of a replacement. Something a bit more challenging.  Looking to later in the year when I hope to make my Level 3 certification flight, I realized that flight will result in a number of firsts for me, if I am successful.  It will be the highest, probably just shy of 13,000′, and the fastest, Mach 1.5.  However, that is all being done by sheer brute force of a 75mm M3100 motor.  Certainly there must be a way to finesse some of these.  I started playing around with some simple designs and simulations with the quick realization that I could go a lot faster with far less motor.  So my goal is to do Mach 1.8 with a 38mm motor.  This is actually fairly easy as well so, I added a little twist.  I want to do this with a tube-finned rocket.

I spent yesterday evening searching for good information on the specifications of various materials used to make the airframes.  There really is a bit of a void here and I think I see an opportunity to make a contribution.  I’m going to make several, at least 4, identical rockets that differ only in the materials used and see how they perform.  There is quite a range of specifications too which should make this interesting – perhaps even exciting if material limitations are surpassed in flight testing.  A tube-finned rocket is ideal in this respect for several reasons.  The tube fins create a lot of drag and will be put to the test, structurally, when the rocket is pushed through Mach 1.  I plan to choose a fin geometry to accentuate that. The geometry of tube-finned rockets spreads the loads in such a way that my ability to achieve uniform glue properties and proper bonding of the fin to the main body tube should not be the limiting factor – at least for the weaker materials.

Right now my list of tubes includes: LOC/Precision tube, Blue Tube, G12 fiberglass epoxy, and Carbon Fiber epoxy.  I may add Quantum tubing after a little more study to see if it warrants inclusion. The initial consensus is that CF is the obvious choice – lighter weight than fiberglass and stronger.  G12 will certainly work but is the heaviest.  G12 is a safe bet.  LOC tube is standard thick-walled kraft paper tubing.  It is the lightest and also the weakest.  Most people expect it to fail at high speed.  Blue Tube will be interesting.  It is strong and light, lighter than CF epoxy, but begins to yield much earlier that CF. All of these tubes have the same wall thickness so, this should be a fair test.

I plan to use motors in the Vmax series from Cesaroni (although the White Thunder and RedLine series have interesting thrust curves).  These Vmax motors burn for less than one second with very high thrust.  In these minimum-diameter, high-speed rockets powered by high thrust motors, weight is of the essence.  The lighter it is, the faster it will go with a given motor and rocket geometry.  Lighter rockets will not go as high as the heavier rockets, however, because more of the energy put into the system ends up as momentum in the heavy rocket rather than being “wasted” pushing the air out of the way with the lighter, faster rockets.  I could have decided to use mid-thrust longer burning motors but, that would be mainly a test of the drag differences between the rockets as much as it was about structural stability.  I could select altitude as the metric but, that would favor heavier rockets.  The proper metric must be chosen for this test and I think it will be top speed – fastest rocket wins.  I want to see which material is the lightest that will survive.  You can think of this another way.  The lighter the rocket, the greater the fraction of the total thrust that must be dissipated as drag (i.e., stress to the structure).  The lighter materials will be tested harder than the heavier ones.

This should be fun!

20110102

Flight Log: 20110101

January 1 brought good weather for flying rockets.  My club SEVRA had obtained permission to fly at Fentress Naval Auxiliary Landing Field and an FAA waiver to fly to 10,000′ so, I decided to go fly rockets on New Year’s day.  Dana, Eva, Steve, Kelly, and Spear also came along.  Eva and Spear built rockets the night before and flew their Estes Gold Streaks several times.  Eva also flew her HiJinks.  To start the day/year off, I flew my Big Daddy on an E28-7T.  Although the simulations indicated an altitude of 1100′, the rocket only went 835′.

I flew my first dual deployment today. I modified my BDR 4.0 by adding an electronics bay and installed a Featherweight Raven 2 altimeter. The ejection charges were constructed from a 1.5 cc centrifuge vial, a Q2G2 igniter, and 1 gram of FFFG black powder. The Cesaroni H225 White Thunder motor delay was set to 1.5 seconds past the predicted apogee as a back up. The flight went without a hitch, perfectly straight up. The yellow rocket was stunning against the unusually haze-free, deep blue sky.  On the H225 motor, the peak acceleration was 11.5G and the maximum velocity was 346fps.  Apogee was measured at 1264′ and was, once again, higher than simulation. The max speed and altitude both support a CD lower than I’ve been using and much lower than calculated. Because of southerly winds, a lot of the rockets flown were headed for, over, and occasionally into the trees so, I decided to use a smaller parachute. The rocket was flown without a drogue.  The apo charge separated the rocket and the resultant descent rate was 50 fps. The main parachute was set to deploy at 500′. The decent rate on the main chute was 25 fps and the rocket hit a concrete taxiway. Modest damage was sustained but, the rocket was repaired this afternoon and is ready to go once again.  Despite the high descent rate and damage, I think the larger chute would have carried it into the trees. All in all, this was a good start to the new year.

20110101

Level 1 and 2 Certifications

Time for a rocketry update. I’ve been building quite a few rockets, each intended to be used in my Level 1 or 2 certification attempts. I built a LOC/Precision Vulcanite first but, on an H motor it looked like it would fly at least 2000′ – a bit high for single deploy at our site. I then built a Performance Rocketry Lil’ Rascal. For various reasons, I was still looking for another design, one that could be used for both Level 1 and 2. Two weeks before my planned Level 1 attempt, I saw an article for a BDR 4.0 and decided to build one. The article indicated a very high CD, 2.4, that would result in very low flights on both H and J motors.

I flew the BDR 4.0 on an H90 on November 6, 2010 at our Boy Scout Rocket-Ree event. NAR president Trip Barber was present and I asked him to be my Level 1 certification official. The flight went perfectly but there were indications that the rocket went much higher than expected. Unfortunately, I did not remember to turn on the altimeter and had no flight data. During the following week, there was extensive discussion among club members as to what the CD should be for a rocket like the BDR 4.0. There was a wide range of opinion, simulation results, and a void of published work on the CD of tube-finned rockets.

BRD 4.0 on a J285 for my Level 2 certification flight

BDR 4.0 on a J285 for my Level 2 certification flight

With great uncertainty as to what the CD actually was, I decided to go for my Level 2 certification two weeks later, November 20, 2010. I passed the written portion of the test with a perfect score and was antsy to fly before the winds were predicted to become unfavorable. I had selected a J285 motor and had run many sims. My expectations were for an apogee of between 2000′ and 2500′ with a modest range of optimal delays. I split the difference and went with a delay in the middle of the predicted range, 8 seconds. I should have known something was amiss when the igniter did not go very far into the motor but, I guess I was fairly nervous. With a puff of smoke, the rocket failed to come to life and sat on the pad. Jeff Goldstein, my certification official, offered me a spare and I made certain the igniter went all the way in the second time. This time the motor started and the rocket roared off of the pad. Once again, it seemed to go much higher then expected. The parachute deployed near apogee in a strong wind. I watched the rocket descend slowly and drift far off behind a row of trees. We jumped in the back of a pickup and headed off to the NE corner of the field. After a brief search, we located the rocket in a field of winter wheat and in perfect condition. The successful flight meant I had passed on to Level 2. I did remember to turn on the altimeter for this flight. The BDR 4.0 flew to 3010′! Follow up simulations could replicate this performance only if the CD was a rather low 0.67.

20100910

Rocketry

When I was in grade school I started flying model rockets. I won’t say how long ago that was, but I will say that a C6 was the biggest motor you could buy. I do remember when the D’s and E’s were introduced. It was a simple hobby back then and I had a nice big park across the street where I could fly them. Fast forward to today, I’m getting back into the hobby along with my daughter (7th grader). I built a couple of small Estes and Quest kits to revive my modeling skills. These are small enough to fly from my big yard. Well the bug bit. I found a club in the area that flies out of a Navy auxiliary landing field. Poking around some of the rocketry websites, I see that the hobby has changed quite a bit. Folks are flying L motors or bigger, FAA waivers are required, and the rockets have electronics or computers that monitor the flight and deploy a series of parachutes at specified points in the flight. This is just the sort of techno-hobby that I like to get into. I have a few mid and high power kits that I’m building and have set the goal of achieving Level 2 certification. I plan to document my progress as well as review some of the products I’ll be using.

20100723

AviStack V2.0 Released

Just a quick note to announce that AviStack version2 has been released. You can get it here. The web site has all of the details on what new features have been included.  Make sure you read the user manual.  It is the only way to learn about all of the new features and how to use them.  There is more goodness to come in the near future.  I’m working on a new deconvolution routine among other things.  I hope you enjoy it.

20100424

How to Install a Solar PV Array – Part 1: Planning

This is the first in a multi-part series documenting what we hope will be the successful design, planning, installation, and evaluation of a residential solar photovoltaic array.  There are two main types of solar power installations: battery systems and grid-tie systems.  I chose the latter since we will not have to purchase or maintain a large number of batteries.  Instead, the electrical grid and our local utility will act as our battery.  This also gives me the ability to produce only a fraction of our power while purchasing what we need in excess of our own generation capacity in the usual way.  Our choice does not affect much of what you’ll see and learn in this series, however.

I’ve been watching the performance of photovoltaic (PV) panels improve and their price drop for a few years now.  Commercially available PV panels with efficiencies of 15% are on the market at reasonable cost.  Recent developments in power inverter technology allow for an economical and efficient inverter to be coupled directly to each individual panel.  I’ll address each of these shortly.  The recent federal rebates covering 30% of the cost finally pushed us over the edge and I will be placing a modular, expandable PV system on our home.  This first installment will cover how to set realistic goals for system performance, how to assess your site, and on-line tools to help with some aspects of the system design.

How much power do I need?

We originally had an electric water heater, oil furnaces and average efficiency air conditioning in our home.  I began charting our energy usage month by month beginning in 2007.  That year we used 22,000 kWhr of electricity. Over the next two years we replaced the electric water heater and oil furnaces with high efficiency natural gas units.  We also replaced the Air Conditioning units with more efficient 14 SEER ones.  Our incandescent lamps were upgraded to either compact fluorescent or LED lamps.  Doing those upgrades reduced our annual electricity usage to 15,800 kWhr or by nearly 30%.  I suspect there are other things we can do to lower our usage, like getting rid of the old refrigerator in the garage.  The point I’m trying to make here is that you need to estimate how much power you use in a typical year and that there are a number of things you can do to reduce your usage.  Installing solar power is not cheap and you need to do some homework before you decide to spend money on a new system.  Our power usage has been pretty stable since the upgrades and I feel that I have a good estimate for what we typically use in a year.

The state we live in, Virginia, has fairly good regulation of the utilities and has put in place reasonable laws governing how utilities have to work with residential customers who wish to generate their own power.  This will certainly vary from state to state.  In VA, we cannot generate power in excess of 10kW of what we use.  This means we cannot push more than 10kW of power back onto the grid.  Practically speaking, this means we probably should not plan to generate more than 10kW of peak power.  We are allowed to generate more than we use in any given month with the excess being carried over from month to month.  We are never allowed to carry over more than we use in a year.  Anything beyond that we provide to the utility for free.  You will need to read up on the regulations applicable to your specific location as this information will be used later.  Given the fact that fluctuations in solar energy due to the weather can cause year to year changes of 10% or sometimes 20% in certain locations, I wanted to limit our solar PV systems size so that we produced no more than 80% of what we expect to use in a typical year.  For our system, that meant we want to produce about 12,500 kWhr per year in an average year.

Where to place the array

The next thing you need to determine is just where are you going to put the solar panels.  If you have a heavily wooded lot, you will be severely limited as to where you can locate the solar panels and how big your array can be.  We are fortunate to have a large open lot that gets very little shade, so finding a place to put a large number of solar panels should not be a problem.   What I will call ‘full size panels’ are typically ~36″ wide and ~64″ tall.  These produce 180 to 230 Watts of power in full sun, depending upon make and model of the PV panel.  There are a lot of different ways to mount solar panels.  The two most common are roof mount and pole mount.  Which method you choose will be dictated by your site, structures, and aesthetics.  We want to mount ours on a roof, but none of our roof slopes have a good southern exposure.  Our best sections of roof are oriented with their  exposure to the south west.  I thought this would be huge problem because common sense indicates that you want your solar panels to face south.  I even went so far as to design a “solar shed” that I could place on our property with the proper southerly orientation.  Talking with a number of local folks who have solar panels and doing some simple searches on the web for information on how much energy you can get from the sun, it appeared that our area has an average of 4.6 hours of sun per day on average over the course of a year.  Doing the math (4.6 hours/day x 200W/panel x 365 days/year = 336kWhr/panel/year) told me that I’d need at least 37 optimally placed panels to produce the 12.5MWhr/year that I wanted.  That is roughly 600 square feet of solar panels or a 20′ by 30′ rectangle.  After spending some time with a tape measure in my backyard, I concluded that I had the room for an array of that size.  With those estimates, I wanted to build a new “solar shed” and put the solar panels its roof with the building oriented perfectly to the south for maximum illumination.

Expected performance – PVWatts

Once I got an estimate on what a new building would cost I began to think about how many more solar panels we could buy instead.  It turned out to be quite a few and I wondered if we had other more cost effective options.  Our house is a rancher with a lot of roof area.  The problem is that the house has the corners aligned with the cardinal directions N, S, E, & W, so the slope of the roof is mostly aligned towards the SW direction.  I was going to write a program to calculate how the annual power output varied when you changed the tilt of the panel (slope of the roof it is mounted to) or the orientation of the roof with respect to south, but I thought that someone had certainly already done the calculation.  Indeed they had.  I found a couple of journal articles which concluded that the orientation relative to true south was not too important.  After thinking a bit about the ecliptic, the length of the day as function of season, and how the power output varied with the cosine of the angle between the position of the sun and the vector normal the plane of the solar panel, I could see why this might be true.  A little more searching led me to a really neat online tool called PVWatts that calculates the power output of a solar panel.  PVWatts is extremely useful and pretty easy to use.  By clicking on a map of the US (a version covering Europe also exists) and filling in some values on how big your solar array is and how it is oriented, PVWatts will calculate the average month by month output an total annual energy production at your location.  It even includes the average local weather for cloud cover and the  variations in solar cell efficiency as a function of temperature.  This is exactly what I needed to size my solar array and evaluate the several possible installation locations.  You can save a lot of time by skipping the map clicking if you save the URL of the form that follows.

Relative change on output as a function of tilt

Relative change in output as a function of tilt

I ran a series of simulations for my location.  The first was to see the effect of varying the tilt of the solar panels.  From my reading on the subject, the consensus was that you wanted to tilt the solar panel to match the latitude of your location, in my case 37 degrees.  Other reading indicated that a tilt of less than the latitude would produce the maximum annual output.  My roof has a 10/12 slope or a tilt of 40 degrees. I ran PVWatts several times changing only the tilt of the array from 0 (flat on the ground) to 90 degrees (standing vertically as though mounted to a wall).  The first figure shows the relative monthly energy and annual energy output relative to a solar panel tilted to match the latitude.  What you can see in the figure (click the figure to see the full sized version) is that as the panel tilt is reduced, the power output increases in the summer months and decreases in the winter months.  The opposite it true as the tilt increases.  At my latitude, the sun goes almost directly overhead in summer and the power output of a panel tilted to 90 degree drops close to zero.  The last point on the graph is the total annual power generated.  It shows that over the course of a year, the total energy output varies only slightly for tilts within 10 degrees of the local latitude.  The tilt alters the amplitude of the seasonal variation.  You can use this to your advantage if you wish to change the amount of power generated in summer vs winter.  Based on my power use history, we use 2.5 times more power in the summer than we do in winter.

Relative change in output as a function of orientation

Relative change in output as a function of orientation

My second set of simulations explored what happens when you do not orient the panels to face due south.  The results of this came as a complete surprise.  Summer power production changed very little.  The reason for this is, during the summer, the sun travels over more than 180 degrees of azimuth.  It rises north of east and sets north of west.  The solar panel can only see 180 degrees of sky, so there is a range of orientations where the solar array will receive the maximum illumination.  What happens is that panels oriented slightly to the west produce their power later in the afternoon than those oriented due south.  At my location, orienting them to the west of south actually produces more power presumably due to a diurnal asymmetry in cloud cover and temperature.  My house roof is oriented almost exactly to the SW (221 degrees, green line in the figure).  With this orientation, the power output is reduced by only 20% in winter, but is still more than sufficient to supply almost all of our electrical needs.  The real important result is that putting the solar array on my existing house roof reduces the total annual energy generated by only 7%!  That means we have to add only another 2.5 solar panels to make up for the difference (40 instead of 37).  The extra cost is less than $3000 as compared to 10 times that for the cost of build a new “solar shed”.  This was a huge revelation.  PVWatts also includes some real world parameters for efficiency of the inverter, losses in the power wiring, and light loss due to dirty solar panels.  Based on the results of the PVWatts calculations, we are going to need to size our solar PV array at 9.2kW if we want to produce 80% of our electrical needs.  PVWatts will also calculate the annual savings based on your cost of electricity.

Panels, inverters, & mounts

PV panels come in a wide variety of sizes, voltages, and total power.  Depending upon which direction you plan to orient the panels, the panel length is a critical dimension to consider when deciding which panel to buy.  I plan to have one small array of 12 panels mounted on the garage and another 30 mounted on the house.  The total is 42 panels.  I put together a little spread sheet to help evaluate the panels and how many I could fit into the available space. On the detached garage I can mount the panels upright (Tall side vertical) and have the mounting rails run horizontally.  With that orientation I could fit twelve 230W panels in 2 rows of 6.  Over on the house, I hit a little snag.  Many panels are just a little over 64″ long, not including the required spacing between panels for the mounting hardware.  Standard roof framing has the rafters on 16″ centers.  The mounting rails are to be placed at the 25% and 75% positions along the length and have to align with the rafter (or you have to add stringers between them) for the lag bolts.  Do the math and you’ll soon realize that these long panels can only be mounted vertically unless you can tolerate having a 15″ gap between the columns of panels.  The available area on my house’s roof dictates that my panels have to be oriented horizontally into 6 rows of 5.  Otherwise, if I mount them vertically I cannot get 30 panels on that roof, only two rows of 12 panels.  You would think that the US manufacturers would have figured this out and made all of their panels shorter than 64″ long.  But no, the Asian manufacturers are the ones that make them the proper size.  For the garage, I decided to go with 230W panels made by Solon.  These are made in the US.  On the house, I’ll have 215W panels made by Sanyo.  Total rated power is 9210 watts.

Inverters are what turn the DC power from the solar panels into 240V AC power that you need to power your house.  Until recently, a typical installation had one or two of these in the system.  You would daisy chain you PV panels serially to produce a rather high DC voltage.  600V is not unusual.  There is nothing wrong with this, however in this arrangement, one under-performing panel (perhaps partially shaded) limits the current output of the entire string of panels.  The ideal way to convert the DC to AC would be to have an inverter for each panel.  This is now a viable option with the new micro inverters on the market.  Enphase makes a micro inverter that can be tied directly to the home’s AC power system.  This saves money since the system does not require a separate Automatic Transfer Switch to isolate the solar array from the grid when the power goes out.  These Enphase micro inverters turn off when the grid voltage is interrupted.  The micro inverters can also be daisy chained to simplify the system wiring.

You can find information on all of the hardware mentioned here in Part 1 over at Wholesale Solar.  Next time, we’ll get into the process of producing a system plan, obtaining the permits, and getting some of the preparatory work done.

20100411

AstroMart Fee

AstroMart has recently started charging a $12 fee to access their Astronomy classifieds and Auction Site.   I wish them a slow painful death deserved by their arrogance.  Obviously, some people fail to grasp Web 2.0.  They had been delaying access to new listings by 30 minutes so “they” could skim the cream.  Then they arbitrarily adjusted the ending times of their auctions so people could not snipe. Now this.  No more for me – I’m outta here and hope you join me.  The opportunity to create a new astronomy-themed Classified/Auction site is upon us.  Anacortes is a close affiliate – perhaps a boycott is in order.  A sad, sad day.  Cloudy Nights runs classified ads. The site can be slow, but it appears to have all of the necessary ingredients – Items and Visitors.

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