Characterictics of the GHE

Characteristics of the GHE - supplementary data to our offer

In the buildings where air parameters have to be strictly observed (for instance in medical services) ground heat exchangers can assist heating and cooling systems (e.g. to cool down condensers in a conventional air condition installation). Even fastidious investors would be satisfied, as they can set up the parameters of their choice by using supplementary devices.
In the buildings where air parameters have to be strictly observed (for instance in medical services) ground heat exchangers can assist heating and cooling systems (e.g. to cool down condensers in a conventional air condition installation). Even fastidious investors would be satisfied, as they can set up the parameters of their choice by using supplementary devices.
The parameters of air, leaving the bed, are characterized be very slow changes in time,noticeable only within a period of several months. These changes are almost impossible to be noticed within a single month. This is an advantage, because the impact of all abrupt changes of ambient temperatures, both daily changes as well as periodical cooling or warming, is reduced.
During rapid warming in winter and in transitional periods, as well as in case of abrupt cooling in summer, the heat exchangers react with some delay. It can happen then, that the parameters of the outgoing air, being used for ventilating purposes, can be worse than the parameters of ambient air. To prevent from such a situation, properly working automatic control (fig. 5) should assure the air is taken from the most favourable source.
In autumn and late summer the temperature of the outgoing air is higher than in winter or spring. In the end of August/beg. of September it can reach 22⁰C, with the ambient temperatures approaching 32⁰C. In the end of February/beg. of March, whith ambient temperature falling down to -20⁰C, the temperatures of the outgoing air can reach -2⁰C, especially during the long and heavy „attack” of frost in January and February. A high inertia of the exchanger can result in shifting „climatic quarters” of the gravel bed temperatures of ca. 2 months in relation to the seasons of the year.

The energetical profits throughout the year. The differences in air temperatures at the GHE inlet and outlet: styczeñ - January, luty - February, marzec - March, kwiecien - April, maj - May, czerwiec - June, lipiec - July, sierpien - August, wrzesien - September, pazdziernik - October, listopad - November, grudzien - December

LOCATION AND REQUIREMENTS: A GHE of a low output can be installed in the foundations wall chambers or under a building, e.g. a garage. It can also be located in the ground beside a building, being covered by a lawn, car park for passenger cars, playground, etc. It can consist of a single chamber (fig. 7) or several chambers (fig. 1).

Fig 5. An example scheme of a ventilating installation for a larger building:

Fig. 5
translation of texts from the drawings:
powietrze zuzyte np. do rekuperatora - used air, e.g. for the recuperator
klimatyzowany obiekt lub pomieszczenie - air conditioned building or room
powietrze zewnetrzne, recyrkul., lub rekuper. - ambient air, recirculation or recuperator

used air, e.g. for the recuperator air conditioned building or room ambient air, recirculation or recuperation. Ground Heat Exchanger
12. Throttler
13. Air filter
14. Heater
15. Intake fan
16. Silencer
17. Air inlet
19. Exhaust fan

A inlet of the ambient air humus native ground distributing bed accumulative bed ground water level
B humus the soil from the excavation
C the soil from the excavation humus

Fig. 6 Various ways to locate the GHE: A-totally embedded; B-partly embedded; C: exposed, at a slope

Fig. 6 In places with superficial ground water a GHE can be located in the following configurations:
a) entire GHE under the ground surface, with only an air suction above
b) partly in-earth GHE, its part located in soil and the rest above the ground level.
c) GHE at a slope, its two sides formed by the slope.
d) (no sketch) The GHE bottom on the ground surface. Thanks to an insulation, going partly several centimeters in the soil, and partly on the slope surface, the isothermes of the ground are brought up to the exchanger, located over the ground surface (Normally to achieve similar thermal effect, you have to increase the GHE volume). The resulting height differences of the ground level can be used to design e.g. a playground.

Fig. 6 translation of texts from the drawings:
ujecie powietrza - inlet of the ambient air
humus - humus
grunt rodzimy - native ground
zloze rozprowadzajace - distributing bed
zloze akumulacyjne - accumulative bed
poziom wody gruntowej - ground water level
ziemia z wykopu - the soil from the excavation

The costs of the GHE, constructed as per fig. 6; prices acc. to KNR*. Fan wattage assumed for a ground resistance GHE of 120Pa.
air flow rate m³/h	3000		6000		9000		15000		25000		110000
exchanger type	A	B	A	B	A	B	A	B	A	B	A
fan engine.[kW]	0,7		1,1		2,2		4,0		8,0		-
net costs of GHE execution (1 €=+/- 4PLN)
Price[PLN]	9537	8326	18358	16703	26668	24552	45882	40021	86556	75888	382420
Assumptions to the calculation: man-hour = 7,50 PLN, indirect costs = 55%, costs of purchase= 12%, profit = 17% * KNR = Material Cost Catalogue, an offical publication, containing costs of materials

Fig. 7
1. inlet of the ambient air, 2. horizontal air distributing duct, 3. the gravel bed, distributing air to the GHE bottom, 4. gravel accumulating bed, 5. air collecting bed, 6. horizontal collecting duct, 6a. air intake to the building, 7. humus-soil, lawn, 8.foamed polystyrene, thickness 100mm, both sides protected by foil, 9.native soil,10. washing installation, 11. draining tube with collecting well - for draining and control in case of a high level of ground water.

Examples of using GHE in ventilating installations:
Cinema, theatre, etc. An exemplary characteristics of the ventilating installation, acting simultaneously with GHE in cinemas, theatres etc. Thanks to air cooling in the GHE, it is possible to reduce an air flow rate pro person down to 20m³/h (30% lower demand for fansand ventilating installations than in case of traditional ventilation without cooling).
A lower air flow rate and preliminary heating of ventilating air in the GHE in winter will result in a 60% decrease of power consumption by the heaters. The air from a GHE can beadditionally heated by a recuperator or mixed with the air leaving a cinema hall (only in theseparts of the building where the used air is free from scents). In such places (cinemas, theatres with a high number of spectators) there is no need for any additional heat source, even with the lowest ambient temperatures. This is made possible by using an automatic adjustment system, in which the temperature of air mixture is being adjusted to the room temperature by means of the throttles (12, fig. 5) and a smooth regulation of the rotations of fan driving engines (fans: 15, 19 in fig. 5).

Fig. 8
translation of texts from the drawings:
Efekty ochlodzenia powietrza w wymienniku gruntowym - the effect of air cooling in the ground heat exchanger
W tym przedziale powietrze trzeba dogrzewac - air has to be heated within this range
Efekty wstepnego zagrzania powietrza w wymienniku gruntowym - the effects of air preheating in the ground heat exchanger

Fig. 8 An example characteristics of a ventilating installation, acting simultaneously with a GHE in cinemas, theatres, concert halls, etc.
designations:
t_p - temp. in the building
t_m- temp. of the mixture or temp. of air after recuperator (70% efficiency)
t_z - t_w- outdoor and indoor temp.
t_gw - temp. at the GHE outlet
t_noz t_noc - air intake temp.