All electric challenges
June 10, 2009

As discussed in the previous post, our goal was to help keep the Chambers home all electric. The previous post explained why we wanted to do this. We were not motivated to construct an all-electric home because we are electric utilities, rather this is how we believe we can achieve a truly Net Zero Energy Home (NZEH).

The two biggest areas that presented a challenge when it came to building an all-electric home were a cooking range and domestic hot water heating.

The Chambers opted for an induction cooking range. The range, while somewhat expensive when compared to a conventional gas range, was easily resolvable. An induction range is electrically powered and uses a magnetic field that only heats the pot or pan. The important aspects are that it heats with the speed and control of gas, but utilizes electricity.

Solving the domestic hot water heating challenge was somewhat more complex. Normally, water comes into the home around 50 degrees F and the hot water tank is set at 125 degrees F. The installer of the ground source heat pump (GSHP) creatively came up with a method that allows the hot water to be preheated up to approximately 90 degrees F. Typically, in an all-electric home, all of that heating would have to be performed by standard electric water heater, which is very energy intensive. By utilizing the GSHP to preheat the water, we only need between a quarter to a half of the energy that would be needed by an electric water heater to heat the water from 50 degrees F up to 90 degrees F thereby greatly reducing the homes energy requirements.

We still need the electric water heater to finish the water heating at an appropriate 125 degree F hot water temperature. This means our domestic hot water heating system actually has 2 tanks. The first tank which utilizes the GSHP for heating at a greatly reduced energy intensity and a second common electrical water heating tank that ensures the water is heated to an appropriate temperature.

What allows this system to be successful is the GSHP can be brought on to provide heat from two different thermostats. This means that if the house thermostat senses a need for heat in the home it can turn on the GSHP to provide space heating and if the hot water preheat tank senses a need for heating it can bring on the GSHP just to provide heat for the domestic hot water.

In future homes with a GSHP, we will be looking for ways to further utilize them to provide more of the homes hot water heating in as least energy intensive way as possible.



Striving for a true net zero energy home
May 27, 2009

Many organizations and builders are making attempts at building a Net Zero Energy Home (NZEH). NZEHs have a variety of active definitions. When a home is claiming to have net zero energy use, you have to ask the following questions:

• Are there any numbers following the NZEH title? It is common to see NZEH 40 or NZEH 20. In reality, those home are striving for 40% or 20% energy use of a typical built home.



• Is the home all-electric? If it is using fossil fuel s (i.e. natural gas, propane or fuel oil), it is very tough to make the net zero energy claim.

All electric is important because there is currently is no way to produce fossil fuels or a renewable equivalent such as ethanol in a reasonable fashion at our homes. Without that capability it is tough to offset any fossil fuel consumed in our homes.

The only other option for a home striving for net zero energy use, but uses fossil fuels, is to produce considerably more electricity than the home uses. In this scenario, the best hope is to have a positive net production of electricity that can be pushed on to the electrical grid thereby reducing the amount of fossil fuel generated electricity needed. How much extra electricity needed becomes a difficult question to answer and goes beyond the scope of this blog post. Suffice it to say it becomes an increasingly expensive way to achieve net zero energy use with what may be considered a questionable method.

Whereas, in an all-electric home using a renewable electric system - like the solar photovoltaic system at the Chambers home - we can feed back into the electric grid during times of excess production to provide electricity that would have otherwise been generated from a non-renewable resource. In this manner, the all-electric home becomes truly net zero because it can offset any fossil fuel generated electricity it may have consumed during times of low or no renewable production with renewable electricity that would have been otherwise generated from fossil fuels.

With the Chambers project, the home owners and design team were dedicated and willing to take on the extra cost and effort to be an all-electric home, so it could be a true NZEH. Our hope is to see what can be done in real world atmosphere with budgets, contractors and homeowners' preferences all considered and meshed to meet the goal of a true NZEH.



Building a cost-effective NZEH using renewable energy systems
April 14, 2009

WPPI Energy created the Greenmax Home initiative with several goals in mind. Among the highest of those goals was to help a homeowner in one of our member communities design and build a net zero energy home (NZEH) that could be replicated on a large scale in a relatively cost-effective manner. The most costly part of the net-zero equation is the implementation of a renewable energy system.

From the start, the Chambers planned to incorporate both a ground source heat pump and solar photovoltaic (PV) panels into their all-electric home. Therefore, we knew going into this project anything that could be done to reduce the overall energy requirements of the home would help when matching a renewable energy system to the approximated consumption and lend itself nicely to the cost effective goal.

Tom and Verona Chambers exhibit a strong conservation ethic, which was evidenced through past utility bills and throughout their initial proposal to participate in this project. It was clear they were eager to learn and to make the necessary choices to live a "green" lifestyle. It was our design team's responsibility to take this enthusiasm and help Tom and Verona build a home that would meet their aesthetic preferences while maintaining our prerequisite to be cost effective.

Through continual communication and feedback, our design team was able to help the Chambers refine their home design so that the heating, cooling, and hot water heating needs of the home could be minimized. This allowed the Chambers to limit the size of the ground source heat pump. This was a critical step because, while the cost of increasing the size of a residential gas furnace to cover additional heat requirements is a few hundred dollars, with a ground source heat pump it can run several thousand dollars.

In turn, this allowed the solar PV system to be scaled back because the ground source heat pump is the single biggest user of energy in the home. By limiting the requirements of the ground source heat pump and the solar PV system, we were able to take a large step toward our goal of building a NZEH in a cost-effective manner.