GB2215357A

GB2215357A - Greenhouse utilizing insulation and reflected sunlight

Info

Publication number: GB2215357A
Application number: GB8804906A
Authority: GB
Inventors: John Hadlow Ogle
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-03-01
Filing date: 1988-03-01
Publication date: 1989-09-20
Also published as: GB8804906D0

Abstract

A building for horticultural use which incorporates glazing on one face only, the Southern face for Northern latitudes. The remainder of the structure is of high thermal mass and/or high thermal insulation to minimise heat loss and maximise thermal storage. A system of moveable insulation panels over the low level glazing are arranged to increase solar collection when open and to insulate the low level glazing when closed. A system of moveable insulated panels form a reflective ceiling, which is raised during periods of sunlight and lowered at other times to create an insulated ceiling and to isolate the glazing. The system may incorporate low level up-lighters for use when the insulation panels are closed reflecting artificial light from the ceiling onto the growing area. The system may incorporate heat storage in the form of a rock bed or by means of phase change eutectic salts. <IMAGE>

Description

LOW ENERGY GREENHOUSE Field This design is for a structure and system for horticultural or other plant growing use which has a low overall heating, cooling and lighting energy consumption.

Background Most indoor plant propogation and growing is carried out in conventional greenhouse structures, which comprise a fully glazed glasshouse to which has been added, over the years, various ancillary equipment to improve performance and/or energy efficiency.

Such ancillary equipment includes overhead artificial lighting, solar screens and blinds, irrigation or hydroponic equipment, fan powered and natural ventilation, computerised automatic controls.

A further common feature of most conventional greenhouse structures is their low thermal mass, which results in rapid reaction to changes in the external environment.

The design which is the subject of this document is for a more energy efficient structure and associated equipment, not a fully glazed glasshouse, and is of particular benefit in more extreme climates such as Northern Europe and could be applied to conventional horticultural use, hydroponic growing and/or plant propogation. Where the design incorporates effective environmental systems then close control of the internal conditions, year round, will permit the growth of a variety of produce including out of season crops.

Design Features The following features, either singley or in combination, are particular to this design. These features are illustrated on the attatched drawings numbers Fig 1 - Fig 9.

1. Building Envelope.

The building envelope is glazed only on those surfaces which benefit from direct sunlight. Other surfaces are opaque and have high standards of thermal insulation. Glazing comprises a multiple layer transparent assembly achieving higher thermal performance than single glazing, while maintaining a high percentage light transmission. The thickness and material of the thermal insulation may vary to suit the particular climate or material availability.

Building Envelope ( continued ) The choice of main structure may vary to suit the site and local conditions and material costs. A basic concrete blockwork building could have the glazing system and insulation and reflector components added. Alternatively, a framed free standing structure could be used. Both these examples are illustrated on the attatched drawings ( Ref 1 - 9 ) 2. Internal Surfaces.

All internal surfaces, where appropriate, have a finish, white, silver metallic or similar, which achieves a high level of light reflection and/or diffusion with low absorption. This arrangement maximises the overall internal light level for a particular light input, whether natural sunlight or artificial light.

3. Variable Insulation.

The structure incorporates moveable insulation panels which can also increase internal reflection of light. The cross section form of the structure may vary to suit a particular application.

The attatched drawings indicate two possible building forms and the associated moveable ceiling and wall panel layout.

A hinged, insulated ceiling operated in separately articulated panels may be included. This ceiling in its "open" position allows the maximum penetration of sunlight. In its "closed" position it reduces the volume of the growing chamber, increases the overall thermal insulation of the effective building envelope and has on its underside a reflective surface. These ceiling panels may be in single sections or multiple hinged sections.

Further insulated panels may be included on the lower section of the glazed facade, which can be closed to increase thermal insulation. In their "open" position they perform as light reflectors, in increasing overall sunlight input.

4. Artificial Lighting and Natural Lighting.

Artificial lighting in conventional greenhouses normally comprises suitably colour rendered lamps suspended above the growing area.

This arrangement results in substantial shading of natural light.

Arificial lighting & natural lighting ( continued ) This design incorporates a reflective ceiling which allows for the use of a wider range of lamps, located at low level, not shading the natural light, acting as up-lighters reflecting and diffusing their light from the ceiling and walls. The choice of light source may vary to suit the particular crop.

This lighting may be used when all the insulation is "closed" to gve 100% artificial light and may be used to supplement natural light with some or all of the moveable insulation "open".

Additional moveable lighting rigs, comprising lamps in frames, may be used for seed propogation.

During cold weather, the artificial lighting may be used at night time during periods of low tariff rate electricity supply.

5. Heat Storage.

Conventional greenhouses have a very low thermal mass resulting in rapid changes in internal conditions or thermal loads as ambient conditions vary.

It is a common situation for excess heat to be available during daytime, but a heat deficit to occur during night-time. In a conventional greenhouse, the daytime excess heat is expelled by ventilation, supplementary heating being required at night to maintain internal conditions.

This design incorporates a system of added thermal mass or thermal heat store.

The high ridge of the building profile increases temperature stratification. Higher temperature air is drawn by fans and ductwork to pass through the thermal store. The store can also reduce over-heating by pre-cooling the store media. This store may take various forms, depending on particular conditions and as illustrated on the attatched drawings, including: --rock bed with air passages - eutectic salt nodules This system to comprise suitably temperature rated eutectic salts, located within an enclosure through which the ducted air is passed. The entire ductwork and heat storage system is so designed as to allow for cleaning and sterilisation by flushing with treated water or fumigation.

6. Environmental Control.

In order to maximise the environmental performance of the structure it would be beneficial for the structure to be served by a ducted ventilation system which can operate in a variety of modes.

These modes of running include: - supplementary heating or cooling from external energy source. Energy source could be direct electric, gas or oil heating, solar heating, solar absorption cooling or heat pumps.

- direct fresh air ventilation.

- re-circulation with possible air to air heat recovery, using flat plate heat exchanges, heat wheels or similar devices.

- warm or cool air to and/or from storage.

- possible carbon dioxide injection.

- humidity control.

The variable insulation, airflow, heating, cooling and lighting may be controlled manually. However, in a commercial situation it is envisaged that pre-programmed, and/or feedback computer based automatic control systems, which are available and which will maximise the energy benefits of the structure and its systems, would be applied.

Drawings The following drawings are included as illustrations of the design principles Drawings Fig 1 - Fig 7 are based upon a concrete block construction of building with rock bed heat storage. Drawings Fig 8 - Fig 9 illustarate the design principles applied to a framed building sheeted in pre-insulated material, profile steel sheeting or similar, having a above ground eutectic salt heat store located in the rear plant room space.

Fig 1 Basic contruction Fig 2 Light Fig 3 Layout for cold climate applications Fig 4 Thermal insulation Drawings ( continued ) Fig 5 Summer/Daytime operation Fig 6 Winter/Nighttime operation Fig 7 Details Fig 8 Main section Fig 9 Ridge & ceiling details

Claims

CLAIMS 1. A building for horticultural or other plant growing use which utilises direct and reflected sunlight to reduce overall heating, cooling and lighting energy having directional glazing with other parts of the building envelope of high thermal mass and/or of high thermal insulation.
2. A building for horticultural or other plant growing use as claimed in Claim 1, which incorporates moveable insulation panels which enable the growing area of the building to be open to the glazing to permit the ingress of sunlight, or to be closed to create an area of lower overall volume which is fully insulated.
3. A building for horticultural or other plant. growing use as in Claim 1 or Claim 2, which utilises the surfaces of the moveable insulation to reflect light into and within the growing area.
4. A building for horticultural or other plant. growing use as in Claim 1 or Claim 2 which utilises materials of hick thermo mass or high thermal insulation or materials of both high thermal mass and high thermal insulation for those sections of the walls, floor and ceiling which are not glazed.
5. A building for horticultural or other plant growing us as in Claim 1 or Claim 3, which utilises low level light sources acting as uplighters reflecting off the ceiling.
6. A building for horticultural or other plant growing use as in Claim 1 or Claim 3 or Claim 5, which incorporates reflective inner surfaces to maximise internal light levels, whether operating under sunlight or artificial light conditions.
7. A building for horticultural or other plant growing use as in Claim 1, which incorporates phase change heat storage by means of eutectic salts located in a chamber forming part of the ducted ventilation system.
8. A building for horticultural or other plant growing use as in Claim 1, which incorporates phase change heat storage by means of eutectic salts located within the growing area.