<![CDATA[neoTerra - Blog]]>Tue, 05 Sep 2017 15:44:46 -0400Weebly<![CDATA[July-August Energy Report]]>Sat, 02 Sep 2017 17:18:07 GMThttp://neoterra.us/blog/july-august-energy-report2017 Energy Use

So far, this summer, we are using about 100 kWh per month more than last year.  Most of this increase is because we've been dehumidifying the basement.  However, we also added a second beverage fridge and a lot more lighting in the basement.

This summer has been somewhat cooler than average and we have used zero AC.

The following diagram shows our 2017 energy use (solid blue line) versus 2016 (dashed blue line).  For fun, it also shows the theoretical energy production from a 6kW solar panel array.  A 6kW array could provide about 85-90% of our summer energy but would, of course, fall far short in the winter when we're heating.

The average over the past four months has been roughly 30 kWh per day.  This in line with the typical consumption for an American household and quite a bit better than a typical all electric home.

For the first 8 months of this year the energy breakdown is shown below:
 - HVAC             26%
 - Refrigerator      9.5%
 - Water Heater  11.5%

Comparison to an Average Home in Georgia

Information from Georgia Power indicates that the typical breakdown for an electric home in Georgia is roughly as follows:
 - HVAC                     50%
 - Water Heater          19%
 - Other and lighting   31%

They go on to indicate that the average monthly cost for an all-electric home is approximately $195.00 per month.

In 2016 our average monthly cost was $136.00 which compares very favorably against the Georgia average.

<![CDATA[Photovoltaics - Solar Power I]]>Sun, 16 Jul 2017 18:22:15 GMThttp://neoterra.us/blog/photovoltaics-solar-power-iIntroduction

The basement is almost complete and the first phase of neoTerra is coming to an end. The first phase has focused on passive design (i.e. passive solar and tight construction) to reduce energy consumption and on the the use of durable, low-maintenance materials to reduce the long term cost and effort to maintain the structure.

The second phase will investigate active system to further reduce consumption or  produce energy.

Last winter we added a high-efficiency wood stove which I hope will provide 1/3 to 1/2 of our winter heat.  This year we will add a small array of solar panels and this post will discuss some of the initial considerations and analysis.

Solar Potential
NREL (the National Renewable Energy Lab) has a treasure trove of information on solar energy. As the following diagram illustrates, the best solar potential is in the Southwest which has an arid climate and uninterrupted sunshine.  The Southeast has good solar potential (about 5 kWh/meter/day) and enjoys a lush climate.   I love Appalachia !!

Georgia - An Anti Solar State

Georgia is a seriously anti-solar state which makes installation of solar panels much less cost effective.  Nevertheless, I enjoy a challenge so I've been spending a good deal of time trying to design a solution with a reasonable payback period.

SolarPowerRocks.com produces an annual "Solar Report Card" ranking all of the states.  For 2017 Georgia comes in at an appalling 37th out of the 50 states.

To make matters even worse, That report card is based on Georgia Power which at least pays full price for any excess energy that you produce. 

Here in North Georgia we are part of Amicalola Electric, a rural cooperative that is only obligated to pay 3.8 cents per kWh for power sent back to the grid.  As a matter of public policy, the Georgia Rural Cooperatives are on record stating "[they] have opposed unreasonable regulations such as the EPA's Clean Power Plan (CPP)".

To put this in concrete terms, Georgia Power charges about 12 cents per kWh and pays the consumer 12 cents per kWh for any over production.  If you oversize your array you will at least be compensated and it will not effect the eventual payback period.

Amicalola, on the other hand, charges approximately 10.5 cents per kWh but only pays 3.8 cents for overproduction. If you oversize your array then you are essentially donating 6.7 cents per kW to the utility company.  In other words, if you oversize your array by any significant amount then the payback period will be NEVER-EVER.

Right Sizing

In an environment where you are penalized for supplying energy back to the grid it becomes especially important to optimize the size of your solar installation.  Just as the corporate euphemism of "right-sizing" really means "down sizing", optimization of the solar array always means reducing the array to just below your minimum demand.


There are several aspects or constraints that need to be considered to achieve a cost-effective design in a solar hostile environment.
  • Available Space - what is the largest array that could be installed
  • Minimum Need - what is the minimum amount of solar production that you require (this could be zero if you are only trying to reduce your monthly bill)
  • Minimum Demand - What is the lowest monthly load. 

On the surface this seems pretty straightforward.  However, solar production changes from month-to-month with much more in the Summer when days are longer and substantially less in Winter.  If you live in an arid, air-conditioning climate, then this might align with your needs. But, for the rest of us, it is generally the opposite of what we require.

Let's look at some of the different considerations and constraints.  I will be using neoTerra as a concrete example.  Your Millage May Vary (YMMV).

Available Space vs Production

I hope that it's obvious that the more space you have, the more energy you can produce.  neoTerra was primarily designed as a passive solar structure so the major roof (over the great room) slopes to the North.  A North slope is not suitable for solar production.

We have enough South facing roof over the bedroom wing to carry 20 standard size solar panels.  This will allow a maximum of 5.8 - 6.2 kW, depending on the grade (efficiency) of the panels.

The actual solar production changes from month to month. As an example, let's consider a 6kW array and use the tool at NREL to calculate the approximate monthly production for North Georgia.  Note that the tool takes the latitude, longitude and estimated cloud cover into consideration.  The following diagram shows the estimated production of a 6kW array located at neoTerra on a 2:12 slope roof facing south.

Theoretically, this array would produce about 850 kWh in May (when we need it the least) and about 400 kWh in January (when we need the most).

Minimum Need

When we built neoTerra we installed two separate circuit panels. One supplies the critical circuits such as the well, refrigerator, microwave, some lighting and networking. The other panel supplies everything else.

We have been monitoring the use of both panels for over a year and have established that we use approximately 350 kWh/month for the critical circuits.   We would like to have enough solar power to run the critical circuits during an extended (several day) power outage.
  • In the event of a real power outage we would probably use a bit less power than what we have recorded... For example, I doubt that we would be watering plants or taking long, cold showers during a power outage.
The following chart indicates that a 6kW array (the dashed yellow line) would be sufficient to power all of the critical circuits (the red line) during the lowest solar production months and would have have a substantial surplus during the higher production months.

The conclusion is that a 6kW array would be more than sufficient to meet our minimum need.

Minimum Demand

As mentioned earlier, this topic is not a concern if you live in a state / utility that pays you a fair price for the energy you produce.  But, here in Georgia, I want to meet my Minimum Need while avoiding overproduction, if possible.

The following chart shows the theoretical output of a 6kW array versus our actual energy use over the past two years.  The theoretical array would produce slightly more energy than our minimum months from 2016 and slightly less than our current use in 2017. A 6kW array appears to be optimal.


A 6 kW array would likely meet our minimum needs in the low production Winter months and would not significantly overproduce in the Summer months.

<![CDATA[Spring 2017 Energy Report]]>Sun, 16 Jul 2017 12:34:12 GMThttp://neoterra.us/blog/spring-2017-energy-reportJune Energy

In the Spring, Summer and Fall we typically use much less electricity than in the Winter.

Last year (2016) June and September were our lowest months.  This year we are averaging about 100 kWh more each month which is a 10% - 15% increase.  Most of this increase is because we are now running the basement mini-splits in dehumidify mode to reduce the moisture.

In June, for example, the temperatures were very pleasant and we didn't use any AC.  However, we had 6.8 inches of rain and the average outdoor humidly was 83.6%. In the basement the humidity levels were even higher.
In May and June we used 97 kWh and 54 kWh for dehumidification respectively. For the first half of July we are running at about double that rate.   Going forward, I will have to anticipate using about 100 kWh per month for HVAC in the warmer months.

That being said, our energy use is still fairly low for an all electric home. 

  • May      997 kWh   -   32 kWh/day
  • June     866 kWh   -   26 kWh/day

The Best Laid Plans ... or Mama and the Three Bears

When we were designing the house I didn't anticipate that humidity would be such a problem on the lower level.  After all, it is a walk out basement with patio doors and large windows.  I imagined that we would get plenty of fresh air through the doors and windows.

I did not anticipate the BEARS.

Mama bear has again made her den somewhere just down the hill from the house (it is quite steep and heavily wooded so I haven't ventured down to look).

They visit several times a week and sometimes spend the night behind the woodpile or come up to the front porch to get a drink from the birdbath.

The cubs are so CUTE.   There are actually three cubs but I can never seem to get a picture of all three together.

Mama especially enjoys rummaging through the carport to find things to play with.  She likes scattering empty pots, dragging the garden hose off into the woods and chewing on bags of mulch. 

She also seems to enjoy sitting in front of the heat pump and letting the hot air blow on her.  I can't imagine this feels good but I'm not going to argue with Mama!

In Conclusion

So... getting back to the point;   we don't leave any doors or windows open at ground level when we aren't in the room.   It's better to spend a little more on HVAC than discover a confused/angry bear in the basement.

<![CDATA[Winter 2016 Energy Report]]>Sun, 04 Jun 2017 15:45:27 GMThttp://neoterra.us/blog/winter-2016-energy-reportAs usual, I am way behind on updates to the blog.  The heating season ended in April and it's June already.   We have been busy working on the basement and I've started on design of a solar panel array that will go on the roof... but that's a topic for a future post!

Wood Stove

We installed an Osburn Matrix high efficiency wood stove in December but, with the basement still under construction, we hardly used it this past winter.  We consumed roughly 1/2 face cord of mixed hardwood from January through March.  That's so little I'm not going to try to calculate the effect on our energy use until next winter.

On a side note, our heating cost has been so minimal that the stove will never pay for itself in reduced heating bills.  However it has 4 big plus factors:
  • It provides a backup heat source if the power goes down.
  • We live in the forest and the wood is free.
  • It heats very quickly
  • Great ambiance

We used left-over / scrap galvalume siding to make reflective panels behind and to the side of the stove.  I really like the way it turned out and I'll post more details in a future blog.

2016 Heating Season

This year I've decided to include October and April in the heating season report.  We don't use a lot of heat in either month but they average about 250 HDD each and together account for 10-15% of the annual heat load.

For comparison the following graph shows HDD by month for Winter 2015 and 2016.

Both of the past two winters have been warmer than average with winter 2016 being close to record warmth.  For comparison, the 2015 heating season had approximately 3413 HDD while this past heating season was only 3022.

The second graph shows the energy used for heating by month for both years.

The total energy used for heating was 3330 kWh in 2016 compared to 4358 kWh in 2015.  Put another way, our total cost for the 2016 heating season was less than $350.00.  
<![CDATA[2016 Energy Report]]>Wed, 08 Mar 2017 20:15:08 GMThttp://neoterra.us/blog/2016-energy-reportWow, it's already March and I'm finally getting around to the 2016 Energy Report.  So... here it is.


First, for those of you just tuning in, the neoTerra project is our home and it is also a living experiment in sustainable design and energy efficiency. We strove to use durable, low-maintenance materials and we utilized recycled or recyclable materials wherever practical.

The house is all electric based on a philosophy that it will eventually be cost effective to produce our own electricity using solar panels but it will never be practical to make home-brew propane.

The house is a passive-solar design with an expectation that we will be able to receive 30% or more of our winter heating from the Sun.  We use Diakin mini-split heat pumps for the remainder and we recently installed a high-efficiency wood stove to supplement the heat pumps and provide backup in the event of a power outage.

The house has roughly 4000 square feet of conditioned space (2000 on the main level shown below and 2000 in the basement level).

The house is located in the North Georgia mountains at an altitude of 2800 feet. The climate here averages about 8 - 10 degrees cooler than nearby Atlanta so heating is a larger factor than air conditioning.

This is an engineering experiment of sorts and we installed an array of temperature sensors in the ceilings and floors to capture detailed data on the actual performance of the passive solar design. 

As an example, the picture below shows the current, real-time temperatures on the main level. It's 4:00 on a bright, sunny day and the concrete floors receiving sun (i.e. to the south) are in the mid to upper 70's while the shaded areas are in the mid to upper 60's. The floor in the guest bedroom is at an amazing 87 degrees!  This is free heat.

I'll discuss the passive solar design in greater detail further down in this report.

2016 Energy Report

2016 Climate Data
Since heating is our single largest use of energy it's important to consider the actual climate data for the year. Our historical average (14 years of data) is 4069 Heating Degree Days (HDD) and 825 Cooling Degree Days (CDD).

2016 started out close to the historical average with January slightly colder than normal and March slightly warmer.  After that, we had the warmest summer on record and a mild winter. Overall, we accumulated 3717 HDD (9% warmer than average) and 1054 CDD (28% warmer than average).

The following chart shows the 2016 HDD, 2016 CDD and the respective historical averages. The dashed lines show the historical averages from our climate model and the solid lines show the actual data for 2016.

2016 Energy Use
The next chart shows the total energy used as well as the amount used for heating and air conditioning. The total energy used was approximately 13000 kWh (about $1300.00) while the total for HVAC was 4539 kWh (approximately $450.00).

It's no surprise that we use a LOT more energy in the coldest months when we're heating and less in the warmer months.

The big surprise this year was how little we used for air conditioning.  This was the warmest summer on record in Atlanta which is about 50 miles to our south.  Good shade, cool mountain nights and superior insulation kept the house comfortable without AC.  We ran the AC only four or five days and spent less than $20.00 on AC for the entire summer.

Heating a roughly 4000 square foot structure for $450 here in the mountains is very good and is actually better than what was predicted by the computer model used in designing the house.

As detailed in earlier posts, we use a TED energy monitor to collect daily data on actual energy use.  Overall, HVAC accounts for about 1/3 of our energy.  The water heater and the refrigerator each consume about $11 / month while the well and electric dryer are almost insignificant.

About 1/3 of the energy consumed is not monitored. This includes cooking, lighting, TVs, computers and so forth.

Passive Solar Performance
The computer model we used while designing the house predicts the passive solar performance based on the following factors:
 - Historical average HDD per month
 - Historical average percentage of sunshine for each month
 - The estimated heat pump efficiency based on the historical average temperature for the month
 - The overall heat load of the entire house

The result is an estimate of the the total energy used (in kWh) per HDD.  Lower numbers indicate better performance (i.e. less electricity consumed per HDD).

The following chart illustrates the results.

The upper gray line shows the amount of electricity that would be used if there was no solar input.  In other words, this line is showing how a conventional house would perform.  Note the results are a bit different for each month since the heat pumps are more efficient in the warmer months (March, April, November) and are less efficient in the colder months (Jan, Feb and Dec).   The performance ranges from approximately 2.5 in the coldest months to about 2.1 in the more moderate months.  Based on an average of 2.25 we would expect to spend approximately $900.00 on heat in an average winter.

The passive solar design model is shown by the yellow line. Heat from the sun pushes the performance to roughly 1.5 in the coldest (least efficient) months and achieves a factor of 1.0 or better in the more moderate months.  Thus, the passive solar design reduces the predicted expense to $508.00, which is a reduction of better than 30%.

Finally, the orange line shows the actual performance for 2016.  This must be analyzed in the context of the actual climate for 2016 shown earlier.

January 2016 was colder than average and the house performed slightly worse than the model (i.e. the orange line is above the yellow line).

February was almost exactly average and here the actual performance is almost perfectly aligned with the model.

March was somewhat warmer than average and the house performed better than the model.

In October and November the house performed much better than the model due to warmer temperatures and a prolonged drought that provided increased sunshine.

As mentioned earlier, the total heating expense for 2016 was only $450.00 which is 1/2 the cost for a similar sized non-passive design.

The results from 2016 show that the computer model is accurately predicting the performance of the passive solar design.

The model could be improved to model the actual year as it progresses rather than comparing against a historical model. This will be a project for 2017.

In 2016, the Sun delivered over 30% of our winter heat and the passive solar design saved approximately 3000 kWh of electricity.

<![CDATA[Drought and Fire]]>Fri, 11 Nov 2016 15:40:25 GMThttp://neoterra.us/blog/drought-and-fireParts of the Southeast are suffering through one of the most severe and  prolonged droughts in the last 100 years. The last time it rained here at neoTerra was on September 19th.  For the first time in history we had zero rainfall in October (the average over the previous 13 years is 4.4 inches).

The drought has hurt our woodland garden projects but that is a mere inconvenience.

The big concern is the many wildfires burning in neighboring counties here in Georgia as well as in Alabama, Tennessee and North Carolina.

The Rough Ridge fire is the largest in Georgia history and has already consumed more than 10,000 acres in the rugged Cohutta Wilderness near Ellijay (the next town north of us). The fire has been burning for more than five weeks has been expanding rapidly over the past 2-3 days.

Smoke plumes from Rough Ridge and from numerous fires in Tennessee and North Carolina are covering the area and extend all the way to Atlanta.  With no rain in sight, the drought and dangerously dry conditions are expected to continue through winter.
<![CDATA[Summer 2016 Energy Report]]>Sat, 22 Oct 2016 13:58:07 GMThttp://neoterra.us/blog/summer-2016-energy-reportWe didn't use any AC in September so I'm going to cover the entire 2016 cooling season in this report.

But first, it's fun to see how far the sun has moved in just one month since the equinox.  The picture on the left shows the sun setting directly to the west on September 21st while the picture on the right shows how far south the sun has moved since then.

September Report

In September we used 672 kWh (just slightly higher than June).  The TED energy monitor recorded 688 kWh so there was only a 16 kWh difference this month.

September racked up 179 Cooling Degree Days (CDD) which was less than June, July or August but was still almost twice the historical average of 93 CDD.  

Summer Summary

This has been the third hottest summer in Georgia in the past 130+ years.  However, temperatures here in the mountains have been pretty comfortable overall.  The warmest day here was 91 on July 3rd.  Since nighttime temperatures have generally been in the upper 60's to low 70's it's been fairly easy to keep the house comfortable without using AC.

Humidity is a bigger problem, and we did run the AC a few times mainly to keep the lower level dry.

The summer months give us a good indication of our average non-HVAC energy use.  From May through the end of September we have used an average of 781 kWh per month.

The two largest items are the refrigerator (about 17%) and the hot water heater (about 14%).  Past data shows that the water heater will double in the winter because the water entering the house is colder.

At the end of the year, I'll do a breakdown that shows the percentage ofl energy used for each major category.
<![CDATA[Happy Equinox - August Energy Report]]>Wed, 21 Sep 2016 14:27:39 GMThttp://neoterra.us/blog/happy-equinox-august-energy-reportHappy Equinox everyone!
Today, the Sun sets directly to the west and we officially transition into Fall.

August Energy Report
At 231 Cooling Degree Days, August was about 10% warmer than the historical average. It was a bit cooler than July and about the same as June.

Although the average temperature in August was only 1 degree cooler than July, it was much more moderate.  The high in August was only 86 while the high in July was 91.  We used zero HVAC during the entire month!

Part of the reason is that the drought finally broke. We had a lot of overcast, rainy days which kept the maximum temperatures down a bit.

                                                                      August Summary

With an average temperature of 92.5 degrees for June, July and August  this has been the third hottest summer in Atlanta in 133 years.  Although temperatures are much more moderate here in the mountains it has been a record setting summer here as well with June, July and August all well above historical averages.

Our air conditioning has been surprisingly low:
  • June       15kWh        $1.50
  • July        43kWh        $5.00
  • August      0kWh              0

This month Amicalola reported 858 kWh versus TED reporting 771.  So, TED under-reported by 107 kWh this month versus over-reporting by 69 kWh in July.  Since this is more than one day of energy use I'm puzzled by the difference and the reversal.

I will have to monitor this for another month or two and then attempt to re-calibrate to two TEDs to obtain better agreement with Amicalola.

<![CDATA[The Star Trek Corridor]]>Fri, 12 Aug 2016 04:00:00 GMThttp://neoterra.us/blog/the-star-trek-corridorTW is a huge Star Trek fan so the lower levels of the house will have a definite Star Trek / Sci-Fi vibe.

In keeping with the Star Trek motif we are calling the levels "decks" like a ship.   In a ship the Main Deck is designated as deck 1 and lower decks are consecutively numbered 2, 3, 4 etc.

So, the main level of the house is Deck 1,  the mid-level of the basement (East) is Deck 2 and the lowest level (West) is "Deck 3".    :-)

The main project we've been working on  over the past few months has been building out Deck 2.

A central feature for this half of the basement is a 20 foot hallway that runs directly beneath the hallway on the main level.

This hallway acts as the "spine" of the house.  The plumbing, electric, Ethernet and coax run through the steel trusses in the ceiling and fan out to the rooms on either side on both levels.

In keeping with our passive solar design, the north side of the corridor is windowless and has two "Cargo Bays" for storage. The south side has Crew Quarters for visiting guests.

The house is built into a ridge so the north side is entirely underground while the south side has windows and a walkout.   Visiting Starfleet dignitaries will have their own private patio!

The picture on the right shows the framing for the two Cargo Bay pocket doors.

Fun With LEDs

I decided to put a suspended ceiling in the corridor so we will have access to the utilities that run down the 'spine'.  But to stay with the Star Trek theme it had to be something interesting.

We started by installing about 100 feet of LED strip lights around the perimeter.  The LED strips come in 16 foot rolls with a self-adhesive backing so they are very easy to install.  This is our third project with LED strip lights and we plan to use them much more in the future.

The strips are powered with inexpensive 12V 'bricks'.

We wanted the ceiling to have a futuristic look and investigated a lot of different suspended ceiling products. We finally decided on translucent  plastic panels from Ceilume.  They come in a variety of different patterns and we selected the simple Polyline for it's classic industrial look.

Main Engineering Blast Door

We wanted something really cool as a focal point at the end of the hallway.  TW designed a fantastic graphic for the door and we commissioned RMwraps in Idaho to produce the graphic.  Click on the pictures below to order your own Star Trek door !
<![CDATA[July Energy Report]]>Thu, 11 Aug 2016 14:19:01 GMThttp://neoterra.us/blog/july-energy-reportJuly was uneventful so this month's report will be pretty short.

TED Upgrade

As I mentioned last month, I added a second MTU to the energy monitoring system and the system can now track and record all the energy use.

The July bill came in from Amicalola yesterday and I'm happy to report that the energy monitoring system is in pretty close agreement with the actual consumption recorded by the electric meter.  In fact, it looks like the TED system is reporting about 6% too high.  I'll see how they compare again next month and re-calibrate the TED system if the results are similar.


At 270 CDD July was about 30% warmer than the historical average.  It was also about 28% warmer than June which came in at 211 CDD.  We had one day above 90 and the rest of the month was in the mid 80's.

We have also been in a drought since February with rainfall only at about 60% of normal. The side effect is more sunny days than normal.  Here's the weather summary for July.

Our total HVAC usage for July came in at 43 kWh or about $5.00.
The total HVAC so far this year is roughly $6.50.   I am smiling as I write this  :-)