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How We Reduced Our Carbon Footprint

8/20/2014 9:11:00 AM

Tags: Renewable Energy, Carbon Footprint, Solar Panels, Hybrid Car

Solar Panel on Roof of House

When I retired from my faculty position at the University of Maine in 2003, I resolved that one of my retirement projects would be to greatly reduce my carbon footprint by making my home and transportation more energy efficient, and reducing my consumption of fossil fuels.  My wife, Lee, supported me in this undertaking, as we were very much aware of the terrible impacts on the environment of fossil fuel extraction, processing, and transport, and the pollution and climate change caused by the combustion of these fuels.   Our fellow humans and other living things depend on this environment, and it our responsibility to avoid harmful impact to them. We didn’t dream at the time that ten years later we would be powering our home and our local transportation largely with solar energy.

We decided to spend a substantial part of our savings and retirement income on this effort to reduce our carbon footprint. We were greatly helped by the residential energy and clean transportation income tax credits provided by the federal government, and the rebates from Efficiency Maine for purchasing and installing equipment in our home to increase energy efficiency and reduce carbon emissions. I am hoping that this essay encourages readers to do some of the same things we did within their financial means.  

As one’s geographic location and living situation have much to do with energy conservation, first I’ll tell you that I live at the end of a dead end, country road in Orono, Maine. Our closest neighbor is about a half-mile away. Our 2,200 square ft, single-story home sits near the top of a gentle slope at the head of a hay field, is sheltered by a forest on one side, and by a row of trees on the other side. Behind the house is our vegetable garden. We are fortunate in being only 3 miles by road to downtown Orono, a town of about 10,000 persons, and a mile further to the University of Maine, and only 6 miles to downtown Bangor, a small city of about 33,000 persons with good shopping areas and other amenities.

Before describing the steps we took to make our transition from fossil fuel to solar energy, I must point out that our transition is not complete. Each year we have been taking one or two long trips by fossil-fuel-powered car or coach and/or airliner, and much of what we buy including most of our food (we garden-produce some) and even the energy-saving equipment we have installed in our home is produced and shipped using fossil-fuel energy. We can and will take further steps to reduce our carbon footprint, but life completely without fossil fuels may not be possible in our economy without full withdrawal from it, and a return to a pre-industrial revolution life style. 

Here are the major steps in our transition (there were also smaller steps, too numerous to mention here):

• Early in the transition we reduced heating oil consumption with supplemental wood heating.
• We installed a solar domestic hot water system.
• We added more home insulation, and “sealed the cracks.”
• We installed a geothermal heat pump system for all home heating and cooling.
• We replaced our oldest all-gasoline car with a hybrid car with much lower gasoline consumption.
• We installed a solar electric (PV) array large enough for all home needs including the powering of the heat pump and an all-electric car.
• We replaced our next oldest all-gasoline car with an all-electric one with no gasoline consumption.   We charge this car’s battery with solar energy, and now use it for almost all of our local transportation.

As I describe each of these steps, where feasible I will indicate the financial costs, and the number of years it will take to pay off these costs from increased efficiencies and reduction in fossil fuel purchases.  Since we installed our new energy systems some of the prices have come down, and now low interest financing is available for some of them, making it possible for younger couples and others lacking our financial resources to take some of the steps we did. First, let me show you a diagram that explains how our new energy systems fit together.

We started in a small way well before retirement by reducing our heating oil consumption with supplemental wood heat, namely with a small wood stove in our living room, as many Mainers do. To distribute this heat to other parts of the house I installed an oscillating fan high on the living room wall, and directed its range to include both corridors leading to other parts of the house. By burning about one cord of oak wood a year, we reduced fuel oil consumption by about 20 percent, for a saving after fuel wood and electrical (fan) costs of about $350 per year, not to mention the comfort of a toasty warm living room. In recent years we have ceased using the wood stove because of the effects of old age on our ability to haul fuel wood.

We had been producing our domestic hot water by the same oil furnace/boiler that heated the house.  In 2007 we further reduced fuel oil consumption by installing solar water heating arrays on our south-facing roof, at a net cost after a rebate of $8,395. However, despite the 80-gallon hot water storage tank, we haven’t had quite enough solar heated water to last through occasional periods of extended cloudiness or when multiple houseguests are taking hot showers the same time of day. Therefore, a small percentage of heating of domestic hot water continued to be by fuel oil.  Nevertheless, the reduction of fuel oil purchases has been saving us about $875 per year, for a pay off period of about 10 years. We’re now more than half way through that period.  Today it is possible to set up a 12-year loan at 2.99% interest for a similar installation for a monthly payment of $75, and a return on investment (R0I) of 10.4 percent.   

At about the same time, we arranged for an energy audit of our then 35 year-old house to learn where we were losing most of our heat in winter, and then we went about sealing and insulating numerous places.   In 2008, we installed about two feet depth of blown fiberglass over the ceiling of our home to increase the ceiling R value to 60.  We could immediately feel the difference. In 2010, we installed three inches of foam insulation in the basement, from the underside of the ceiling and down the inside of the concrete foundation to 2-3 feet below the level of the exterior soil surface. The basement and the upstairs floors became noticeably warmer in winter.  The cost of all this work after rebates was $2,407. I’ll not attempt calculation of the payback period for this expense due to the complications caused by our switch in 2009 from heating with oil to a geothermal heat pump, and starting in 2012 by the powering of the heat pump with electricity from our own solar panels.

 

Slinky in Trench

In 2009 we replaced most of our remaining fuel oil usage with a geothermal system, namely, a heat pump in our basement, and heat exchange pipes outdoors and underground.  Six-thousand feet of polyethylene pipe, coiled like a stretched out slinky into three 200 feet long, six foot deep trenches extend under the field in front of our house. By 2011, no surface evidence of the presence of these trenches could be seen. Two small electric pumps in the basement circulate an antifreeze solution in this closed system of pipes, and to the heat pump. In the heat pump, heat is extracted from the solution to heat the house in winter, and heat is added to the solution to cool the house in summer. By pumping the solution around the pipes, this heat is transferred from or to the ground in the respective seasons. At the heat pump, the heat is transferred to or from a forced air ventilation system, heating the house in winter, and cooling it in summer. The heating phase uses the solar energy stored in the ground during the warm time of year, so fundamentally this is a solar system. The system has supplied our entire house heating and cooling since installation. 

Subsequently, we connected the heat pump to our domestic hot water system to use waste heat from the machine’s operation to supplement water heating. Since this system went into operation in August 2009, we have used only about 50 gallons of fuel oil per year for backup hot water heating during cloudy periods, and when we have multiple overnight houseguests. The net cost after a rebate and a federal tax credit for the geothermal heat pump system was $25,495. The replacement of oil house heating and the augmentation of hot water heating replaced about $2,900 worth of fuel oil per year, for a payback period of just under nine years.  Since we installed our geothermal heat pump, much less costly ductless mini-split air-based heat pumps have become practical for supplemental heating/cooling in this climate. They are mounted on outside walls, and are effective for heating and cooling home spaces similar to those that would be heated by an outside wall-mounted propane heater. They are electrically powered, much more energy efficient and cheaper to run than propane heaters, but not as efficient in BTU per dollar in our cold winter as geothermal systems.  

Although our heat pump system nearly ended our fuel oil purchases, it increased our usage of electricity by about $1,000 per year, and that leads me to the next part of the story. Most of the electricity we had been purchasing from the power company had been produced by fossil fuels, negatively impacting the environment. In 2012 we were able to further reduce our carbon footprint by installing solar photovoltaic (PV) panels to produce our own electricity, and by that September we were on line. We installed a 9.36 Kw PV array of 39 panels. Based on our history of electric usage we calculated this array would be enough for all our household needs including the heat pump plus the charging of an all-electric car for 7000 miles of local travel per year. As our south-facing roof was inadequate for this size array, and was already partially occupied by solar hot water panels, we installed a freestanding PV array in the field below our house.    The entire cost of this installation was $28,790 after a rebate and tax credit.  Based on our predicted electricity usage, and current power company rates (equivalent $2400 in annual electric savings), it will take us 12 years to recoup these funds. If power company rates go up, as seems likely, the time will be shortened.   Today it is possible to set up a 12-year loan at 2.99% interest for a similar installation for a monthly payment of about $240, and a return on investment (R0I) of 7.8 percent. Maine is presently lacking a rebate for solar PV installations. If it is returned, these figures will improve.

Producing one’s own solar electricity is complicated by the fact that the sun doesn’t always shine. There are two ways of handling this problem. The first is to install a bank of large and expensive storage batteries in one’s basement to charge up when the sun shines, and to draw electricity from them when the sun is not shining. This is the only option when one’s house is in a remote location off the electrical grid. A more practical and much less costly solution is the one we use.  Our solar array is connected to the grid power line just below our house, and thus we cogenerate electricity with the power company. We meter our solar electricity output to the grid, and separately meter the electricity we draw from the grid at our house.   When we produce more kilowatt-hours (KWH) than we use, as in April through October, the power company credits us for the excess KWH.  When we use more than we produce, as in November-March, we use up our credits. Our goal was to make our solar array barely large enough so that over the year we would wind up not having to buy electricity from the power company. In its first year of operation, the array produced 12,000 KWH of electricity, and is well on its way to producing about the same amount in this second year of operation. With the recent addition of an electric car, we will need another year of experience to see how close we have come to our goal.

Solar Panels

The final part of my story deals with my concern over the use of fossil fuel by our two cars.  I should explain that with our busy lives, and Lee’s and my involvements in different community projects and other volunteer work we have felt a need for separate cars. At our rural location, public transportation is inadequate to get us where we need to go in a timely manner. In 2010, we owned 1987 and 2002 Toyota Corollas, both getting 30-35 miles per gallon (mpg).   The 1987 car was ready to junk and recycle, so in 2010 we replaced it with a new Toyota Prius. With this hybrid car, we have since achieved the following approximate average numbers of mpg of regular gasoline:  winter local 45 mpg, highway 55 mpg; summer local 52 mpg, highway 57 mpg. Spring and fall have yielded intermediate values.  Like all vehicles powered entirely or in part by gasoline, mpg is determined by many factors including driving style. It takes practice, but we have found that slow acceleration, coasting to stops (when traffic allows), timing traffic lights to avoid full stops (when traffic allows), and consistently staying within posted speed limits considerably increase mpg.  Unfortunately, this is not the predominant driving style in our area and elsewhere. Since buying the Prius, we have purchased about 850 fewer gallons of gasoline than we would have purchased for the old Corolla, saving about $3,000, and emitting much less carbon and other pollutants to the atmosphere. By the end of 2015, we will have recouped the increased purchase price of a new Prius over a new Corolla by reduction in gasoline purchases (assuming similar mileage driven).

By November 2013, we were ready to replace our second old Corolla, for the final big step in our energy system. We were burning about 300 gallons of gasoline a year in our 2002 Toyota Corolla and 2010 Toyota (hybrid) Prius, combined. We sold the Corolla, purchased a new all-electric Nissan Leaf, and installed a 240v charging station for the Leaf in our garage. We now plan our local trips to minimize use of the Prius for local travel, and have been able to use the Leaf for over 90 percent of these short trips. The Leaf’s average range between charges is only about 95 miles, about 20 percent more in summer and less in winter. Apart from that limitation, it is a silent joy to use, much simpler and cheaper to run than a gasoline powered vehicle as it has no exhaust system, no gas tank and tank fill-ups, no engine oil to change or cooling water to monitor, and is easy and quick to plug in for battery charges.  A total charge at our station takes 2-3 hours, which we typically do overnight. At a quick charge station it takes only about a half hour, but such repeated quick charges sacrifice battery life.  

Given the range limitation of today’s all-electric cars, and the absence of quick-charge stations at convenient locations along most of the US highway system, these cars are not for everyone. Location of residence is an important consideration. They are most practical for use where most trips are short, as for well-placed rural locations like ours.  A large majority of our local trips for shopping and other activities are within 10 miles of home, with some up to 25 miles from home. These cars are also practical for persons with short daily commutes by car to work. Longer commutes are possible if a charging station is available at the destination, as is provided by some industrial and commercial employers. The availability of a second family car that can run on gasoline for the occasional longer trip adds additional practicality to all-electric car ownership. We still need to use our Prius hybrid for those trips. 

Since the November 2013 purchase of the Leaf, and as of August 2014 we have bought only about 75 gallons of fuel for the Prius to cover our three trips to Massachusetts and the occasional use of our two cars simultaneously for local trips. The cost of the new Nissan Leaf plus charging station, after subtracting the sale proceeds of the old Corolla, and receipt of a federal tax credit was  $25,804 or about the same cost of a new Prius. But the zero-emission Leaf is far superior economically because it is much less costly to run per mile.

I hope that all of the above encourages readers of this article to take some of the same steps we have taken to reduce their negative impacts on the environment. Each reader has unique considerations in deciding which steps to take. Any of the steps will help to reduce the terrible impacts on the earth and fellow human beings of fossil fuel extraction and use.  As mentioned earlier, younger persons than ourselves, and others who lack the money up front for some of these steps, can now obtain low interest loans for some of the home improvements including solar, and can obtain no- or low-cost financing for hybrid and electric car purchases. Solar array rentals have become a popular approach for going solar, but the jury is still out regarding whether rental or financing is more cost-effective.  

I would be happy to discuss how you, too, can reduce your carbon footprint. I can be reached at 207-866-4785 or at ronald.davis@umit.maine.edu. I am not associated with any manufacturers, vendors or installers of these products, and have nothing material to gain from sharing my experiences with you, and discussing how you may be able to take some of the same steps that Lee and I have taken.



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