Solar Photovoltaic Technology

Photovoltaic Solar is the conversion of light into electricity using semiconducting materials that enact a generation of voltage and electric current in a material upon exposure to the sunlight. Light is absorbed, causing the excitation of an electron or other charge carrier to a higher-energy state. A photovoltaic system employs solar modules, each comprising a number of solar cells, which generate electrical power. PV installations may be ground-mounted, wall-mounted, or floating. 

Some hope that photovoltaic technology will produce enough affordable sustainable energy to help mitigate global warming. Solar PV has specific advantages as an energy source:: once installed, its operation generates no pollution and no greenhouse gas emissions and it shows simple scalability in respect of power need. PV installations could ideally operate for 100 years or even more with little maintenance or intervention after their initial set-up, so after the initial capital cost of building any solar power plant, operating costs are extremely low compared to existing power technologies. 

This is why Green Seed Apartments chose to use photovoltaic solar technology to power our building. Not only because it is one of the greenest forms of renewable energy but also because it is cost-effective. Solar technology is the reason why we are able to offer our residents no utility costs. We also have the roof space to install a lot of solar panels. In fact, we will be installing 144 solar panels. 

144 solar panels that produce 400 watts each. This means we harvest 28,800,000 kWh of electricity in 500 hours of sunshine per year. This is not enough to power 1400 apartment units, at a generous 20,000 kWh per year. Yet, we only have 31 energy-efficient units. That’s a lot of free juice for everyone and the neighbors too. You see, Green Seed Apartments isn’t just a carbon-neutral building but we make the whole neighborhood greener too. We have cut wattage throughout the building, so before we even install the solar panels, we are already as energy-efficient as possible. This means that the energy we produce through our solar panels can power not just the units but also our internet, our heating, our battery charging stations, and all of the lighting with a plethora of power left over.

Advanced Framing

Advanced Framing: We have updated the tried and true “24 inches on center” framing layout, to realize an estimated 50% reduction in lumber and labor, without reducing quality or strength. This means that a lot fewer trees will need to be cut down, sawed up, and transported, thereby reducing our transport-related carbon footprint. 

By stacking all key structural components, keeping the entire design “on layout”, and using doors and windows that fit within the layout, we have eliminated much of the lumber typically needed to cut openings and terminate walls. Because the designing of such an efficient 24-inch layout can be rather involved and time-consuming, developers in the last 70 years have opted for the more “flexible” 16-inch layout.

 With energy and material efficiency as one of our primary goals, world-class architects and designers on retainer, and limited scope for our building needs, we are delighted to be able to build in this traditional sound, and environmentally friendly manner. Not only is less lumber used in advanced framing, but thermal bridging is also minimized and more insulation can be used in the thermal envelope.

Energy Use Intensity

Energy Use Intensity: 

Essentially, EUI expresses a building’s energy use as a function of its size or other characteristics. EUI is expressed as energy per square foot per year. It’s calculated by dividing the total energy consumed by the building in one year (measured in kBTU or GJ) by the total gross floor area of the building (measured in square feet or square meters). 

Until recently, multifamily property owners, tenants, cities, and utilities undervalued whole-building energy usage data because this information was not widely known or understood. This is now changing as more citywide benchmarking initiatives target multifamily buildings and stakeholders discover multiple uses for detailed and complete multifamily energy usage data. 

Right now the average EUI for multifamily development in the nation, according to Energy Star Portfolio Manager, is 59.6 kBtu/SF. An energy-efficiency building is considered any building with an EUI lower than 40. 

According to a study done by Glumac, the EUI of Green Seed Seed Apartments at Burnside is projected to be 11.9 kBtu/sf. Buildings that claim to be at the cutting edge of energy efficiency in Portland, Oregon have EUI’s around 19. This makes Green Seed Apartments at Burnside the most energy-efficient multifamily in-fill in the entire Pacific Northwest, and not by an insignificant amount. 

If you want to learn about how we reduced our EUI to be the leaders of our field read it here at our blog about passive solar technology: 

Passive Solar Technology

What is Passive Solar Technology? 

No, it is not using solar panels. Most simply passive solar technology is using the structures and environment around you to decrease heat loss. At Green Seed, we take passive solar technology very seriously. From the roof to each wall, and each window we make sure that passive solar technology is used because not only does it increase the comfort of our occupants but there is no additional power that is used to implement it. 

How we use it: 

  • More insulation in each wall: Fiberglass is about 3 times more efficient, as a thermal insulator than wood. By building our walls on a 24” layout (as opposed to a 16” layout) we have reduced their wood content by about 50%. This amounts to an R-value increase of about 133% for each unopened wall. On top of this, we use thermal break (with an equivalent R-value of 6.2) around the entire wall surface, to effectively double the thermal resistance of the studs, headers, and trimmers. 
  • Sealed and insulated roof cavity: In order to achieve energy efficiency in the roof area, we combine a highly insulated roof cavity with an R-13 thermal break to give the roof maximum energy efficiency. This method has the added benefit of moving the dew point outside the cavity and reducing the potential for dry rot. 
  • Triple pane windows: We use triple pane windows to further reduce the loss of energy. 
  • Radiant Heating: Building for comfort is a very important part of home design. However, air temperature is only part of the equation. It is more important to use Mean Radiant Temperature (MRT) as a baseline on how the building will function. Simply, we want the air temperature and the temperature of surrounding objects to contribute equally to overall comfort (e.g., if the floor is cold and the air temperature is 80 degrees, you will still feel cold)

Geothermal Heating

What is geothermal energy? 

Geothermal energy is a renewable energy source because heat is continuously produced inside the earth. People use geothermal heat for bathing, heating buildings, and generating electricity. Geothermal energy is old technology. Ask any early caveman who lived in a cave. Geothermal energy is contained in the rocks and fluids beneath the earth’s crust and can be found as far down as the earth’s hot molten rock, magma. 

How do we use it?

We’ve laid the ground loops for the geothermal heat exchange pipes at Burnside Boardwalk, our 31unit net-zero affordable housing development on E. Burnside. A ground loop is a series of pipes buried underground at a depth where temperatures stay consistent year-round. It serves as the critical link allowing geothermal heat pumps to use the earth as a heat source or heat sink, to assist in both heating and cooling the entire building.

How does a ground loop work?

Just a few feet below the ground’s surface, the earth maintains a steady temperature of 50 to 55 degrees, no matter what the outside air temperature is. This difference allows the earth to act as a heat source in winter and a heat sink in summer.

A geothermal heat pump (located inside the Building) captures this energy by circulating thermally conductive regular water through the buried pipes in the ground loop. In winter, the water absorbs heat from the warmer earth and the heat pump carries it into the building, where it enters a heat exchanging system and is used to warm your home. In summer, the same process is used to capture heat from the building and release it into the cooler ground, leaving every unit comfortably cooler.

Horizontal Ground Loop

A horizontal ground loop is installed over a wide area of ground and requires enough space to dig trenches hundreds of feet long and 6-10 feet deep. Horizontal ground loops can only be used when adequate yard space is available and trenches are easy to dig.  We have installed 500 feet of pipe in 16 loops,  8 loops buried at 14 feet deep, and 8 loops buried at  7 feet deep.  When we start to backfill around the foundation we will bury an additional 6 loops at an average of 6 feet deep.  This will give us a total of 11,000 feet or a little more than 900 feet of pipe per ton.

To install a horizontal system, workers utilize trenchers or backhoes to dig trenches 5-10 feet below ground and then install a series of plastic pipes that comprise the geothermal heat exchanger. They will then backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes. A common practice is to coil the pipe into a slinky shape to fit the loop field in a smaller area. While doing this reduces the amount of land area needed, it will require the installation of more pipe. We have used a combination of straight pipe and a modified slinky approach.

Is it actually energy efficient? 

The U.S Environmental Protection Agency (EPA) has called ground source heat pumps the most energy-efficient, environmentally clean, and cost-effective space conditioning systems available. Its source is the almost unlimited amount of heat generated by the Earth’s core. Even in geothermal areas dependent on a reservoir of hot water, the volume taken out can be reinjected, making it a sustainable energy source. 

Experts say geothermal energy is cleaner, more efficient, and more cost-effective than burning fossil fuels, and it can reduce our dependence on foreign oil. Geothermal power plants emit 97% less acid rain-causing sulfur compounds and about 99% less carbon dioxide than fossil fuel power plants of similar size. (IEA) Other forms of heat production are more carbon-intensive, more energy-intensive, and less efficient.