Rainwater harvesting is
the collection and storage of rainwater. This system is going to take
rainwater and save it to use for our home. The system will use rainwater
that comes off of the roof from a storm and then is captured and stored
underground. It is then disinfected and filtered. We will then use this
water for our toilets, sinks, and other water appliances.
Earth Berming
Earth
Berming is pushing earth (soil) against the side of a building for
external thermal mass to reduce heating and cooling loss and to easily
maintain indoor air temperature.
Solar Thermal Systems
Solar
thermal energy (STE) is a technology for transforming solar energy into
thermal or heat energy. This may be used to heat and cool buildings and
to heat water for use in buildings and swimming pools. Most solar
thermal systems are composed of three main parts: solar collector,
insulated heat transport piping, and heat storage. In colder climates,
some type of freeze protection system may be needed.
The three
types of solar collectors used in residential applications are:
flat-plate collectors which are typically used for solar pool heating,
integral collector-storage systems which pass cold water through the
solar collector to heat the water (used in mild climates), and
evacuated-tube solar collectors which consist of parallel tubes
containing a refrigerant.
At CEED, a closed evacuated-tube system
is used. It consists of 30 elongated tubes located on the roof in two
solar collectors. Because the climate in Rocky Mount can drop below
32°F, propylene glycol, an antifreeze solution, is heated in the solar
collector. The heated liquid is circulated from the solar collector
through a heat exchanger connected to a storage tank. Potable water is
warmed by the tubes containing heated propylene glycol. The heated water
then goes to the storage tanks, while the cooled propylene glycol is
piped back to the solar collector to be reheated. An added benefit of
this closed system is that it requires little maintenance and can also
be used for heating and cooling the building through the energy recovery
ventilation system.
Solar Orientation
Passive
solar design places a home or building to take full advantage of the
sun’s energy for the heating and cooling of the living spaces. The
building should be oriented so that the long side faces south and the
short sides face east and west. Areas most frequently used for living
should be located on the longer south side. Facing due south maximizes
the incoming solar energy, or insolation, to provide natural lighting
and free heat. The three key components of passive design are:
appropriate solar orientation, the use of thermal mass, and appropriate
window placement and ventilation. Earth berming can also be integrated
into the system.
The CEED building is oriented due south with
operable windows to allow incoming radiant heat and ventilation as
needed. All of the exterior walls are poured concrete to provide thermal
mass. The interior floor is a six inch insulated pressed concrete slab
that stores free heat. Floors of this type may be stained or covered
with conductive material such as tile. Heat stored in the floor (thermal
mass) is released back into the interior during the night.
To
moderate temperature extremes, CEED is earth bermed on the north, east,
and west facing sides. This feature allows the building to be cooler in
the summer and warmer in the winter. Since CEED is located in the
temperate zone, it is not necessary to berm the north side higher than
six feet, and the east and west sides two to three feet.
Photovoltaics
The
word photovoltaic comes from the words photo meaning light and volt
referring to a measurement of electricity. Photovoltaic cells, sometimes
called PV cells or solar cells, are made up of silicon. Solar cells
supply energy to items that are powered by batteries or electrical
power. Sunlight strikes the solar cell, causing electrons to move which
produces an electrical current. Conversion of solar energy to electrical
energy occurs instantly.
Two different types of solar electric
systems can be used to generate electricity for homes and buildings. The
stand-alone system uses batteries to store electricity produced by PV
cells. This system does not connect to the utility power grid and
requires more maintenance such as refilling water in the batteries. The
grid-tied system uses an inverter in the building to convert Direct
Current Electricity (DC) into Alternating Current Electricity (AC),
which allows it to be used by the building and other consumers on the
grid. When there is low demand for electricity in the building, excess
PV power flows to the grid causing the utility meter to turn backward,
essentially selling electricity back to the utility company. This policy
is known as net metering. The only maintenance with the grid-tied
system is the adjustment of the solar panels to the changing angle of
the sun throughout the seasons.
On the roof of CEED, solar panels
are made of racks of cylindrical tubes mounted horizontally and packed
closely together. These cylindrical panels absorb solar energy from
every direction (direct, indirect, and reflected light); therefore, the
panels do not have to move to track the sun. The panels also allow wind
to blow through them. A second type of solar panel is a flexible PV film
that is laminated to the flat pan surface of a metal roof panel. The
thin film system is similar to a cool roof surface because it acts as a
solar reflectent. In addition, there is a tracking flat (rigid) panel
which can move along two axes. This panel is mounted atop a pole, near
the building, and constantly tracks the path of the sun. The tracking
system is the only device that uses electricity from the grid-tied
system. The remainder of the electricity is sold back to the power
company.
Wind Energy
Wind
is air in motion caused by the uneven heating of the earth’s surface by
radiant energy from the sun. Wind is a clean, renewable energy source,
free to use, and produces no air pollution. Energy can be extracted from
the wind by a rotary device called a wind turbine. As the wind pushes
against the blades of the wind turbine, it makes them spin. This powers a
generator to produce electricity. A wind turbine consists of blades,
shafts, gears, a generator and a cable. Working together, these parts
convert the wind’s kinetic energy to mechanical energy and then to
electrical energy. The size of a turbine and the speed of the wind
determine the amount of electricity produced. While a small turbine may
power one home, large turbines can produce enough electricity to power
1000 homes. Wind farms or clusters of wind turbines provide power to the
electricity grid which is the network of power lines across the entire
country.
The CEED campus contains two different wind turbines. The
horizontal axis turbine is a Skystream 3.7 rated at 1.8 kW for use as a
residential turbine. A small inverter in the hub converts to AC power
and feeds it directly to the building. The second turbine, Windspire, is
a vertical axis turbine appropriate for urban, suburban and rural
environments. Electricity is immediately available to the building.
Although the campus is not an optimum wind site, the turbines do feed
electricity to the grid providing a reduction in the energy bill for the
school.
Geothermal Heat Pump
A
geothermal heat pump is an underground heating and/or cooling system.
It transfers heat from the ground in winter and into the ground in
summer using a liquid refrigerant that is circulated through long loops
of underground pipe. Typically, this is a closed loop system. Based on
the arrangement of the loops, there are four types of closed loop
geothermal systems. The horizontal ground loops are shallow and may be
400-600 feet long. Vertical ground loops are used in extreme climates,
in rocky terrain, and where space is limited. In this type of system,
loops of pipe are dropped into deep holes. Slinky coil geothermal ground
loops are popular in residential systems because they are more
economical and are shorter than traditional horizontal ground loops.
Geothermal pond loops require a pond or lake that is at least a half
acre by eight feet deep, where the coils of pipe are installed in the
bottom of a body of water. Geothermal systems are twice as efficient as
conventional heat pumps and 50 percent more efficient than gas furnaces.
This is due to the liquid to air heat exchange instead of the air to
air exchange in the average heat pump.
At CEED, the slinky coil
geothermal ground loop system is used. Slinky coils, rather than
straight pipe, are laid out along the bottom of a wide trench. Propylene
glycol, a refrigerant, is pumped through the loop system. Ideally, this
system will rarely be used as the primary source of heating and cooling
due to the efficiency of the CEED building.
Overhangs and Green Roof
Roof
overhangs are like putting a cap on the building. They are structures
that are designed to block the high-angle summer sun, and allow the
lower winter sun to penetrate the building. Overhangs are the most
effective on the south facing side and the upper level of a multistory
building. There are several types of overhangs, which may include
awnings, shade screens, or trellises.
The trellises at CEED are
permanent structures that extend from the roof overhang. The material
used in the trellises is a recycled structural composite (RSC) made by
Axion International from a blend of recycled plastic. The durable RSC is
stronger, lighter, and will not rust, splinter, rot, absorb moisture,
or leach toxic chemicals into the environment. Because it is impervious
to water, insects, or marine parasites, RSC can be used in making
infrastructure products for bridges.
A green roof is a roof that
is partially or completely covered with plants. A green roof can be
characterized according to the weight load on the building. An extensive
green roof has a lower load bearing capacity, while the intensive type
can support lawns, walkways, playgrounds, and even ponds. The extensive
roof is lower in cost to create and maintain, needs no irrigation, and
is covered with mosses, sedum, herbs and grasses. The intensive green
roof is higher in cost and maintenance, needs regular irrigation, and
uses plants such as perennials, shrubs, and trees.
At CEED, shade
is provided in the summer by the planting of deciduous vines such as
grape, wisteria, clematis, or jasmine on the trellises. Landscaping
around the building includes ground plants, hanging baskets and large
pots. In the winter, after the leaves drop, the sunlight can freely
enter the windows and warm the building.
The CEED building
utilizes the extensive green roof system, where sedum is grown along the
upper roof line ridge. Although it does not completely cover the roof,
it does provide a model for capturing precipitation and absorbing heat.
It also serves to filter pollutants and carbon dioxide from the air.
PassivHaus
The term PassivHaus refers
to a specific standard of construction for buildings which provide
comfortable, healthy living conditions year round. It is considered to
be passive because it heats and cools itself without an active heating
and cooling system.
The basic features of PassivHaus construction are:
Passive use of solar energy with southern orientation and shade
Good insulated exterior shell
Energy efficient window glazing and frames
Building envelope to maintain air-tightness
Passive pre-heated fresh air
Highly efficient heat recovery system (air/air heat exchange)
Solar collectors or heat pumps to supply hot water
Energy-saving appliances
CEED
is a passive solar building oriented to the south with an overhang and
trellises for shade. The floor is pressed concrete with six inches of
insulation. The building uses a highly efficient geothermal heat pump
for heating and cooling. Solar thermal energy is also used for heating
the water and for heating and cooling through the energy recovery
ventilation system.
Constructed by Structures Design/Build of
Roanoke, Virginia, CEED has been certified by the Passive House
Institute US for meeting PassivHaus energy-efficiency standards. It is the first public school building in the country to meet PassivHaus standards and the only building in the world where design components are taught in the building.
CEED has been built to meet and exceed PassivHaus specifications.
To be certified, the building must use 90 percent less energy for
heating and cooling and have 70 percent lower carbon dioxide emissions
than a typical building. The air to air heat exchanger is 93 percent
which exceeds expectations.