Indirect Gain Sunspace Convective Loop

8/11/2019 Indirect Gain Sunspace Convective Loop

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Building

Science3

B

BUILDING SCIENCE 3B

Lecture 4: Passive Solar Design Systems

INDIRECT GAIN, ATTACHED SUNSPACE & CONVECTIVE LOOP

Lawrence Ogunsanya

[email protected]


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Indirect gain (Thermal storage wall) Design

Overview The indirect transfer of solar heat into the space to be heated

from a collector that is coupled to the space by an un-insulated, conductive or convective medium (suchas thermalstorage wall or trombe wall).

A thermal storage wall is a passive solar heating system inwhich the primary thermal storage medium is placed directlybehind the glazing of the solar aperture.

The outer surface of the massive wall is painted a dark colouror coated with a selective surface to promote absorption of

solar radiation. Solar radiation absorbed on the outer surface of the wall is

converted to heat and conducted (or convected in the case ofthe water walls) to the inner surface where it is radiated to theliving space.


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Thermal storage wall/Trombe Wall

with Vents


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Thermal storage wall/Trombe Wallwith Vents

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Exterior Interior


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Salt lake city, Utah, USA
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Operation of Trombe Wall

Sunlight hits the darkened mass wall and absorbed heat moves

slowly across the wall The inside surface temperature peaks 6-8 hours after the midday

outside surface peak

Operational vents allow optional controlled air circulation into

the space during the day Overhang reduces wall sun exposure during the warmer months

Vent added to outside at the top can drive warm air out in the

summer and bring cooler air from a north vent

can be used as part of a North-facing greenhouse

may be retrofitted to existing houses with water, concrete, brick

or stone construction


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Water Wall

Water walls are thermal storage walls that use containers of

water placed directly behind the aperture glazing as the thermalstorage medium.

The advantage over masonry walls is that water has a volumetric

heat capacity about twice that of high density concrete;

it is therefore possible to achieve the same heat capacityavailable in a Trombe wall while using only half the space.

The high thermal storage capacity of water walls makes them

especially appropriate in climates that have a lot of sunshine.


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Water Wall
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Thermal Storage Walls or Trombe Walls

Advantages:

Eliminates glare

Lowers temperatureswings in room

Vents allow partition of

energy into daytime and

nighttime heating Sun hits entire mass

Best for sunnier climates

Disadvantages: More expensive and less

efficient than direct gain

Wall requires speciallysized foundations andinstallations.

The wall can block view

and daylight. Occupies valuable spacein

building


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Attached Sunspace Design Overview

Sunspaces also known as green houses are spaces designed for

passive solar gain that are attached to the north side of the

building.

There are many possible configurations for a sunspace but all

of them share certain basic characteristics:

Sunlight enters the sunspace through north facing glazing that

may be vertical or inclined or a combination of the two and is

absorbed primarily on mass surfaces within the enclosure;

the mass may be masonry or water in appropriate containers

and is generally located along the north wall and in the floor.

Operable windows and circulation vents in the north wall

provide for heat transfer by thermal convection from the

sunspace to the living space.


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A sunspace may be semi-enclosed by the main structure such

that only the north facing aperture is exposed to ambient air,

or may be simply attached to the main structure along the

north wall of the sunroom, leaving the end walls exposed.

The temperature in a sunspace is not thermostatically

controlled but is generally moderate enough for humanhabitation during most of the day and appropriate for growing

plants year round.

Attached Sunspace Design Overview


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Sun spaces come in three configurations

Attached Sunspace

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Sunspace Conceptwith mass wall added


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Attached Sunspace


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Attached Sunspace


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Attached Greenhouses or Sunspaces

Advantages: It acts as a buffer zone to

reduce heat loss from the

adjacent living spaces. The sunspace can be used

for growing house plantsand food.

Provides additional living

space. The sunspace can become

an aesthetic asset to ahouse.

Disadvantages:

Construction of sunspace with

high performance glazing can

be expensive.

Thermal performance

depends greatly on how it is

operated and used.


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Convective loop Design Overview

A convective loop system uses a flat plate solar collector to

heat air or water. The heater air or water then flows by natural

convection to directly heat a living space or to a thermal

storage area.

One of the systems has a vertically mounted collector, and the

other has the collector mounted at a tilt.

Either of these systems can be mounted on an existing wall, so

they are quite suitable for retrofit applications.

Either of these systems needs two openings into the building,

one at the top of the collector for heated air flow into thebuilding,

and one at the bottom of the collector for cool air flow from

the building into the collector.


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Some applications use a window on one floor for the upper

opening and a window on a lower floor for the bottom

opening.

Other names used for any of the convective loop systems are

isolated gain and thermosiphon system.

Convective loop Design Overview


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Convective loop

Building

Science

3B
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Convective loop

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Advantages: It is the most thermally

efficient of all the passive

system types

It can be relatively

inexpensive to install and

construct

The homeowner has

complete control of the heat

gains and losses

Disadvantages: The TAP can be an aesthetic

liability

Convective loop only provides

heat, unlike direct gain and

sunspace which provide light

as well as heat.

The system needs periodic

cleaning and maintenance.

Not effective in denselypopulated and developed

areas

Convective loop


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Questions

Indirect Gain Sunspace Convective Loop

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