GB2598885A - Systems for a greenhouse - Google Patents

Abstract

A method of sustainable water and heating control for a greenhouse 12 comprises the steps of: a) catching, filtering and storing rainwater; b) preheating the rainwater before use in a plant growing system 16; c) storing large hydroponic nutrient solutions indoors; d) capturing solar energy and storing it in a water accumulator T4 with water stratifying devices 66, 68; e) capturing the heat derived from thermophilic composting and storing it in the water accumulator T4; f) distributing heat from the hot water accumulator T4 into a radiant floor 30, g) capturing warmed air from the heating of photovoltaic panels 22 during daylight hours as well as hot air under the roof 46 of the greenhouse 12; and h) redirecting warm air for space heating at the bottom of the greenhouse or storing that heat in the ground 26 on the south side of the greenhouse 12. The filtered rainwater in tank T3 is heated from heat distributed from the accumulator T4.

Description

Systems for a Greenhouse

Field of invention

The present invention relates to methods and systems for collecting, conditioning, storing, and distributing rainwater and solar heat to maintain a stable indoor temperature in the greenhouse all year round using a combination of solar bioclimatic design and integrated renewable energy systems.

Background of the invention

in the past 10 years, an increasing number of urban public and private spaces have been reclaimed for projects growing food all over the world. Unless large capital and operating expenditures are invested in building and operating a high tech urban farm with complex ciimate control, the vast majority of such urban food growing projects, should they be social community food growing projects or simple allotments, are mostly disused during the coldest months of the year.

To maintain good and sustainable productive growing environment for plants all year round, it is important to maintain the following seven conditions within acceptable limits: i. Enough space to grow, 2. Adequate temperature range, Enough sun...ght, 4. Enough water supply of acceptable quality, 5. Adequate ventilation, 6. Enough nutrients, and 7 Enough time to develop.

Plants generally* thrive in an environment as close as possible to their optimal conditions maintained without excessive variation. Indeed, when those conditions are too extreme, a significant portion of chemical energy produced by photosynthesis is diverted to adapt to that environment instead of growth, reducing greatly yields and weakening plants, and increasing their vulnerability to all sorts of disease.

While the growing season can be extended with a standard greenhouse from 6 to 9 months in latitudes around 500 North, the temperature still often needs adjustment with.. supplementary external heat sources in colder months and air conditioning in hotter months. This is without mentioning that, despite providing a good protection from excessive wind and rain, diurnal temperature variation can often reach over 20°C in most locations outdoors and 10°C inside a greenhouse, which then become detrimental to efficient plant growth, as well as comfort of gardeners.

Previously proposed systems and elements thereof are described in CN105519380 Tianjin Zhenfa Technology, SE201550129 Skanska -3 -Sverige, EP1936314B1 Martin Kraus, 01204335450 Yu An Gang, KR1012933752 Jeon Gong Gil and U$2011061832 Albertson Luther D. While each plant has its own specific needs with regard to each 5 of the seven conditions described above, it is an aim the present invention to address providing adequate water supply and maintaHrHng moderate temperature, avoiding extreme conditions and buffering variations with properly sized water and solar heat control system (collection, storage and distribution). 10

Summary of the invention:

Accordingly the present invention is directed to a. method of sustainable water and heating control for a greenhouse comprising the steps of: a) Catching, f......tering and storing rainwater; b) Preheating the rainwater before use in a plant growing system; c) Storing large hydroponic nutrient solutions indoors; d) Capturing solar energy and storing it in a water accumulator with water stratifying devices; e) Capturing the heat derived from thermophilic composting and storing it in a water accumulator; f) Distributing heat from hot water accumulator into a radiant floor; -4 -g) Capturing warmed air from the heating of photovoltaic panels during daylight hours as well as hot air under the roof of the greenhouse; and h) Redirecting warm air for space heating at the bottom of the greenhouse or storing that heat in the ground on the south side of the greenhouse.

Advantageously the stored rainwater is further filtered before being warmed-up.

In a preferred embod ment the thermophi ic composting air supply is utilized. to heat one of more plant beds with plants that needs higher temperature all year round, such as tropical plants.

Preferably a radiator is supplied with hot water from a. central accumulator.

Advantageously the exhaust heat from a stove is harnessed to be 20 transferred and stored in a central hot water accumulator.

In a preferred embodiment one or more automated top openings in the greenhouse release excess temperature to the environment to avoid overheating. -5 -

Preferably the function of a preheating tank is directly done by the hot water accumulator.

A solar bioclimatic greenhouse is designed to maintain microclimates for plants-to grow all year round with water and air temperatures maintained for good plant growing conditions without the need of using any fossil fuel (or electric) heating or cooling systems. The method of the present invention is centred around the use of thermo-mass properties of the ground and water to capture, store and distribute heat intelligently using solid bloclimatic design with integrated renewable energy systems, as well as a modular space configuration depending on seasons (solar heat capturing and heat conservation measures in colder months, or sun radiation protection and natural cooling measures in hotter months).

Brief description of the attached drawing:

An example of the present invention will now be discussed in relation to the accompanying drawing, in which: Figure 1 shows a schematic process flow diagram, representing air and water flows between each element of the water and heating system of a greenhouse, according to the present invention.

Detailed description:

A. Rainwater catchment, filtration, and storage: Rainwater falling on outdoor spaces is absorbed. by soil and plants. During intense or prolonged rainfall, excessive rainwater is drained into a pond 10. Water from the pond 10 can then be used to irrigate outdoor plan-during prolonged periods of dry weather.

Rainwater falling onto a greenhouse 12 is collected through gutters 14 and filtered by gravity through a series of filters: a coarse filter FF1 (5mm mesh) to remove any large particles, followed by a medium sand filter FF2 (Effective size of 0.5mm with uniformity of less or equal to 4). The rainwater is then stored in a large insulated storage tank located preferably partially underground to maintain cool temperature and outside of the greenhouse. The tank TI is sized to either meet an indoor 15 hydroponics system's 16 peak water demand for the maximum dry weather period recorded past 5 years or calculated maximum rain water volume collected through roof catchment area over a rolling 5 days period over the same past 5 years, whichever is the smaller number. During exceptional prolonged downpour, an overflow 18 of the tank T1 is connected to the outside water pond 10.

Whenever the water level in a header tank T2 for clean water irrigation, located inside the greenhouse 12, drops below a 25 predetermined Level, the rain water from the tank Ti is then pumped by a pump PI via a second set of filters FF3 (i.e. 100pm

-I -

filter) into the header tank T2. The pump P1 is then stopped once the header tank T2 is topped-up. The header tank T2 can be equipped with a potable water top-up system from the mains supply if available.

B. Rainwater distribution: Water is used as irrigation water for standard (or improved) indoor raised beds or green walls, as well as to make nutrient solutions for the different hydroponics systems, such as a wicking system, nutrient film technic (NFT), aeroponic systems, whichever has been chosen. While the irrigation could be fully automated, it is not initially recommended as this means more reliance on instrumentation such as humidity sensors, actuated valves, electronic control panels and hence making the system more prone to break down. As the greenhouse size targeted is relatively small (less than 150m?), automation can remain limited to a few basic functions, such as tank water level control.

C. Greenhouse temperature control system in winter: To maintain a temperature inside the greenhouse 12 around 19°C in winter (when average temperature outside is around 4°C in temperate climates like London), the methodology to design the greenhouse sustainable heating system follow 6 steps described here: 1. Design and integrate the optimal solar bioclimat c architectural features that the greenhouse 12 requires, -8 -depending on the climatic and environmental. conditions. The solar bioclimati-architectural features are passive solar systems that do not need any powered equipment. These features typically allow the climate indoors to be more resilient to daily temperature fluctuations and focus on energy conservation. The output of this step is to design a greenhouse 12 enveloped with sufficient insulation to maintain a specific heat loss to a maximum of 90 kilowatt hours of primary energy per square meter of floor surface per year (90 kWhpe/m2/y) but ideally to less than 50 W4hpe/m2/y; 2. Size and integrate a. mix of different solar heat collectors 22, 24 that work best in winter conditions on and around the greenhouse envelop, that can harness at least the yearly total heat loss calculated in step 1; 3. Size and integrate a. max of ground and water heat storage banks 26, 28 that have a heat capacity to store enough heat harnessed during sunny days by solar collectors 22, 24 in step 2 for a heat autonomy of a duration to be decided by the gardener, but typically no less than 4 consecutive days of overcast.; 4. Size and integrate a mix of heat distribution systems 30, 32, 44, 64 and 70 of stored heat for either space or water heating purposes; 5. Repeat the calculations of steps 1 to 4, to ensure that the interactions of all components of system have been considered; and 6. Finally test the designed system with different climatic scenarios (prolonged heat waves or prolonged freezing conditions) with dynamic thermal simulations and adjust if required sizing components accordingly until the temperature control system can maintain the average daily indoor air temperature of between 18°C (winter) and 23°C (summer) with daily maximum air temperature variation not exceeding 4°C, i.e. for a. daily average indoor air temperature of 19°C, the air temperature would be maintained between a minimum of 17°C in the early hours of the morning, and a maximum of 21°C at peak heat during the day. This greenhouse climate control system also ensures that indoors water tanks are maintained all year round at temperatures between 18°C and 21°C.

In the coldest months, when daily average outdoor air 20 temperature drops below 15°C for over a week (i.e. in London, this is typically between the beginning of October and the end of April), the active heating system described in the present invention can be activated. A building management system (Automatic control system, includingsensors, actuators, control 25 panel, PLC, network, SCADA, remote access) would perform tie -10 -function of coordinating each element of the heating control system to maintain stable temperature in the greenhouse 12.

The following 4 paragraphs describe the 4 different croups of components forming such a sustainable greenhouse heating control system, namely bioclimatic heat control system, active heat collection systems, heat storage and heat distribution systems, and how they interact with each other.

D. Solar bioclimatic heat control (Passive heat control): Solar bioclimatic architectural. principles are tne foundations on which an active heat control system is developed and integrated onto, to improve even further the greenhouse climate without the use of any fossil fuel or electric heating or cooling system.

The solar bioclimatic architectural principles and corresponding greenhouse component selected in this method and system are summarized here: One of the four sides of the greenhouse is oriented to face the geographically south ideally exactly but with a deviation to geographical south to no more than 150 west or east. This side of the greenhouse 12 has the function of bringing in as much light and heat in the coldest months of the year and the opposite side of the greenhouse 12 exposed towards the north (±15°) is insulated completely without glazing to protect it from cold northern winds.

2. The greenhouse footprint has a rectangular shape. The footprint S of the greenhouse space should not exceed 150m2 and the ratio between overall footprint S and height H sguared is to follow the relationship S/H2 -4.24 with a deviation of no more than 0.4 (S/H2 to be between 3.84 and 4.64). This ensures that the greenhouse 12 has a compact shape minimising heat loss as well as a pleasing aesthetic shape.

The greenhouse envelop needs to have some high thermo-mass inertia to capture and accumulate day sun' s radiative heat and release it slowly overnight towards the inside of the greenhouse with an 8 to 12 hours depbasing. In this design methodology and system, thermo-mass inertia comes from both earth and water elements. The greenhouse designed in this methodology and system has two high thermo-mass elements considered for that purpose: a. The lower section of south side (typically the first meter frem ground level) is built with a minimum 30cm thick of rammed earth covered with glazing on the outside with a sealed gap of 1 to 2 cm. The glazing on the outside is protecting the radiative heat captured by the wall from loss to wind, as well as -12 -trapping heat in the space between the glazing and the wall.

b. The greenhouse roof is flat with a small slope between 2% and 5% towards the north side. Between 10 and 20% of the total roof surface close to each of the 4 edges is constructed as a green roof 32 with a minimum of 1-meter width from the edge of roof. What is described as a green roof is a roof that supports vegetation growth. This part of the non-glazed roof also acts as a solar heat capturing component as well as insulation layers.

4. Overall good focus on sufficient insulation and elimination of thermal bridging in north wall, roof and underground to rn...n.im.ize overall heat loss.

5. Use of appropriate geo-sourced building materials (i.e. rammed earth, adobe bricks, clay plaster rendering, lime, etc.) or bio-sourced (straw bales, recycled paper or cotton insulating board, fibre boards, wood, etc.) materials with focus on breathable materials with good moisture buffering value which help to regulate indoor humidity and have also good insulation properties.

6. Use of buffering space(s) without any heating or air conditioning on the north side of the greenhouse 12 to -13 -limit heat loss from south side space (s) which can receive heat from heat distribution systems. In the present heating control system, the electrical control panel and other motorised equipment such as pumps and fans are mostly grouped in a technical room (space) located on the north side of the greenhouse 12.

Use of well positioned climbing vegetation and/or deciduous trees that partially shade the greenhouse 12 in the summer months, but do not obstruct light in winter. A space in front of the south side of the greenhouse 12 is dedicated to growing several annual high climbing plants that would provide some screening from summer sun, but would be removed in winter to allow the low sun's rays to penetrate the south side glazing and south facing sun's radiation to be captured in the wall below E. Active Heat collectors (and heat sources and heat carrying fluid/material) : 1. Solar water heating collector (solar radiation captured, and heat stored in water) Solar water heating. collector 24 such as evacuated tubes solar collector heats the water within a close water recirculating 25 loop 25 with a pump P4 to transfer and store solar heat into the water heat storage tank.. T4 vie heat exchanger HE5. The water is -14 -obviously only heated on sunny day, and so to stop tank 14 from losing back heat at night or on cloudy days directly through the solar heat collector 24, the pump P4 is automatically stopped in dependence upon day light conditions.

2. Thermo-voltaic solar panel The thermo-voltaic solar panel 22 produces electricity from the photovoltaic panels. The "waste" heat from solar radiation is captured by an air flow on the back of the panel 22 via a heat exchanger 34. The resultant warmed air can then be used for drying or contributing to space heating in the greenhouse 12 via on end of connecting pipe 36. In the meantime, the heat taken away avoids the thermo-voltaic solar panel 22 overheating and so maintain optimum conditions for efficient electrical conversion.

The warmed air can hence be directly utilized within the greenhouse 12 in winter by one end of a pipe 36 and valve 44, or heat stored underground via valve 64 and a network of clay pipes 26, which acts as heat exchanger between the ground and air, storing the excess heat from summer and releasing it in winter.

Whenevpr there is no need to cool down the thermo-voltaic system 22 (i.e. during overcast days or during the night) and bring outside fresh air into greenhouse 12, the opening of valve 40, whach is in the pipe jo.n. g the panels 22 to the connecting -15 -pipe 36, can be varied depending on demand and closed if necessary, thus air within greenhouse 12 is only recirculated via the valve 38 by air fan FIN1 to provide ventilation for the plants (even on overcast days and sometimes when necessary 5 during night too). Whenever thermo-voltaic panels 22 are active and hence generating heat, the valve 40 can be opened up depending on demand to bring into greenhouse 12 warmed fresh air directly via valve 44 or conditioned air through the ground to air heat storage 26 by opening the valve 64 (and closing the 10 valve 44).

3. In the greenhouse roof hot air within greenhouse 12 is accumulated under the pitch 46 of the roof. An insulated and radiant heat reflective indoor glazing curtain 20 and an insulated outdoor glazing folding blanket can be deployed during cold nights to limit heat loss through glazing.

4. Thermophilic winter composting system: A thermophilic winter composting system 52 can be activated in colder months when outdoor daily average air temperature drops below 15°C for over a week, i.e. for London area, this typically corresponds to the period between the beginning of October and early May.. The slow decomposition of a mixture of food waste and woody waste (other carbohydrates polymer such as lignin, hemicellulose, and cellulose) by aerobic bacteria provides a small extra background heat source. The compost temperature can -16 -indeed reach a stable temperature of about 55°C. The waste heat can be harnessed in two ways: o via a closed water circuit 48 with a recirculating pump P5: heat exchanger E59 located around the thermophilic composting system 52, which takes the waste heat from the compost and discharges it back into the heat storage tank T4 via another heat exchanger HE6; and o via an opened air flow 50 driven by a fan FN2 which draws a smallair flow into the thermophilic composting system 52 which charges itself with residual heat and humidity before being discharged onto the underbed 54 of heat loving plants (improved tropical plant bed).

The thermophillc composting system 52 process results a few months Later in the production of a. good compost that can be utilized in the spring of the following year. While in operation, the process needs to be feed a food and wood waste mixture once at least every month.

a Winter masonry heater 56 is using seasoned woody material or simply wood During exceptionally cold days (say less than -5°C for a consecutive few days in London) with prolonged cloudy days that 25 would prevent efficient functioning of the solar hot water collector, a complementary heating source in the form of wood -17 -or pellet-burning stove surrounded with masonry walls such as rammed earth 58 will ensure overall resilience of the heat system against exceptional long and cold weather event of sub-zero degrees Celsius. It indeed would provide instantly radiative and convective heat for space heating, as well as harnessed heat from the exhaust stack via a water closed loop 60 that would transfer heat from the chimney exhaust 62 to the heat storage tank T4 via a couple of heat exchanger HE7 and HE8 and a recirculation pump PO. The stove would help maintaining heat storage tank T4 topped-up during exceptional (low temperature for a few consecutive days) cold event without sunshine, so that heat can be d..strihuted to the greenhouse via the indoor radiant floor 30 and radiators and hence contribute to maintaining a temperature of above a minimum of 17°C within the greenhouse 12.

Heat storage systems: I. Outdoor Ground to air heat transfer and storage The air fan FN1 can extracts both warmer air from under the roof and warmed air from the thermo-voltaic solar panel 22. The warmed air can be redirected through valve 44 to the base of the greenhouse 12 (bypassing the ground to air underground heat store by closure of valve 64) as space heating* to warm the plants up in winter and also bring them a gentle, but necessary air circulation. The warmed air can also be stored as surplus energy underground via a. clay pipe network 26 which act as an -18 -air to ground heat exchanger, before being reinjected back into the greenhouse 12. When there is no solar radiation (cloudy day or night time), the fan FNI can continue to work recirculating air in the greenhouse 12 and conditioning it to near ground temperature. However the valve 40 can be closed to prevent bringing in cool or cold air if necessary, while the valve 38 remains opened, thus the air fan FN1 is only recirculating greenhouse 12 air 2 Indoor Radiant floor 30 The indoor radiant floor 30 brings much greater comfort to gardeners and helps maintaining the first metre of the greenhouse 12 at a more stable and comfortable temperature, which brings more comfort to gardeners working in there.

Masonry heater waifs (therm° mass property of rammed eartni A rocket stove can be placed centrally in the greenhouse 12 and be fired up during the evenings of very cold nights. The rocket stove has two main benefits, firstly a much higher combustion temperature than a regular stove (so limiting the risic of partial combustion and hence possible escape of monoxide carbon), and secondly quick combustion oftypically less than an hour minimises the risk of an unattended fire overnight.

-19 -The rocket stove surrounded with a Layer of rammed earth 58 which stores a portion of the heat from the stove and returns to the space as radiant heat over a 12 hour periods, limiting the need to maintain the stove on during* the night.

4. Heat storage tank T4 Hot water accumulator tank T4 acts as the central heat store for collecting and redistributing heat when needed. Inside the tank, a couple of heat stratifying devices 66, 68 (one for charging 10 66, the other for discharging heat 68) allows for a good stratification of heated water within tank T4. The bottom of the tank T4, is used to charge the tank T4 with heat via all heat exchangers located within the loading stratifying device 66 which lifts the warmed water up and then stores it at the right level in the tank T4 (each layer of different water temperature has a different density, and warm water rises until it finds equilibrium with water of the same density (and hence temperature). Similarly, the heat unloading stratifying device 68 allows for the cooled water to drop within the device 68 without disturbing other water layers with different density and temperature and the water then moves to where the water has the same density/temperature lower in the tank T4. In conclusion all water movement is made inside the stratifying pipes 66, 68 while the bulk of the water in tank T4remains undisturbed and stratified, which boosts the performance of the heating redistribution of the tank T4.

-20 - 5. Pre-heating tank TM Whenever there is a water demand by the hydroponic systems or for any other growing technics water from header tank T2 gravitates through a preheating tank T3 with enclosed water maintained at a temperature between 19°C and 20°C. A heat exchanger HEI inside tank T3 warms the water up to between 15°C and 20°C. Whenever the water in Lank T3 drops below 19°C, heat is provided from the heat storage tank T4 via a recirculation pump P2, a close water recirculation circuit 70 and two heat exchangers HE2 and 11E4. Rainwater from tank TI (or T2) is mainly used to irr gate plants within the greenhouse with warm water, and so tank T3 is used mainly in the colder months when rainwater in storage tank T1 is less than 15°C. In warmer seasons, the tank T3 can be bypassed.

6. Hydroponic nutrient solutions storage tanks T5 The main growing technic used is hydroponic systems with substantial volume of nutrient solution: a minimum of 1m3 of nutrient solution stored in tanks T5 per 10m2 of growing area. This provides an additional greenhouse heat buffering capacity from both water and indoor air temperature diurnal variation. Whenever possible the nutrient solution storage tanks are located underground within the greenhouse footprint and are no more than 2m deep.

-21 -G -Heat distribution systems: The outside face of the south facing wall is soaking-up radiant heat during the day when sun's azimuth position is 5 between 135° and 225° and ic leases trapped heat over the next 12 hours towards the inside of greenhouse 12.

2. Air fans FN1 are operated only during daytime only, or if there is mains electrical power supply or sufficient electrical battery storage, these can also run 24 hours a day if necessary.

3. Air Fan FitI2 is operating continuously from early October to late April or whenever the thermophilic composting system is operational.

4. Tthe Radiant floor 30 (radiant heat plus air convection) is intended to run continuously between early October and late 15 April.

Radiators (radiant heat and air convection) axe intended to run only on coldest days, when radiant floor heat is not sufficient.

6. Thermophilic compost system releases continuously 20 background heat from early October to late April.

7. Masonry heater 58 releases radiant heat overnight or on very cold days for 12 hours renewing every 12 hours only when required.

H. Greenhouse temperature control system in summer: -22 -Protection from over-heating and excess humidity build-up in summer is achieved using the induced passive ventilation, backed-up with mechanical ventilation when prolonged low wind conditions are experienced. The outdoor landscape around the greenhouse 12 also helps to reduce heat island effect. A pond 10 located on the south side helps by absorbing and dissipating extra radiative heat. Daily air temperature fluctuations are partially regulated by an air to ground heat exchange system: air temperature in the greenhouse 12 is controlled via a ventilation system that takes hot heated air from one high corner of the greenhouse 12, cools it via a network of underfloor pipework. 26, the ground to air heat exchanger being locateo outside on the south side of the greenhouse, and redistributes it to another lower corner of the greenhouse house 12 at a cooler

_

temperature.

A further secondary heat dispersion system takes the form of automated rooftop opening to let any excess heat out via passive ventilation

Claims (8)

1. -23 -Claims I. A method of sustainable water and heating control for a greenhouse comprising the steps of: a) Catching, filtering and storing rainwater; b) Preheating* the rainwater before use in a plant growing system; c) Storing large hydroponic nutrient solutions indoors; d) Capturing solar energy and storing it in a water accumulator with water stratifying devices; e) Capturing the heat derived from thermophilic composting and storing it in a water accumulator; Distributing heat from hot water accumhiator into a. radiant floor; g) Capturing warmed air from the heating of photovoltaic panels during daylight hours as well as hot air under the roof of the greenhouse; and h) Redirecting warm air for space heating at the bottom of the greenhouse or storing that heat in the ground on the south side of the greenhouse.
2. 2. A method of sustainable water and heating control for a greenhouse according to Claim I, in which the stored rainwater is further filtered before being warmed-up.
3. 3. A method of sustainable water and heating control for a greenhouse according to Claim 1 or Claim 2, in which the -24 -thermophilic compostihp air supply is utilized to heat one of more plant beds with plants that needs higher temperature all year round, such as tropical plants.
4. 4. A method of sustainable water and heating control for a greenhouse according to any preceding Claim, in which a radiator is supplied with hot water from a central accumulator.
5. A method of sustainable water and heating control for greenhouse according to any preceding Claim, in which the exhaust heat from a. stove is hatnessed to be transferred and stored in a central hot water accumulator.
6. 6. A method of sustainable water and heating control for a 15 greenhouse according to any preceding Claim, in which one or more automated top openings in the greenhouse release excess temperature to the environment to avoid overheating.
7. 7. A method of sustainable water and heating control for a 20 greenhouse according to any preceding Claim, in which the function of a preheating tank is directly done by the hot water accumulator.
8. 8. A solar bioclimatic greenhouse using the method according 25 to any one of Claims 1 to 7.