MINISTRY ENERGY AND ELECTRIFICATION USSR

MAIN SCIENTIFIC AND TECHNICAL DEPARTMENT
ENERGY AND ELECTRIFICATION

METHODOLOGICAL INSTRUCTIONS
FOR CALCULATION AND DESIGN
SOLAR HEATING SYSTEMS

RD 34.20.115-89

SERVICE OF EXCELLENCE FOR SOYUZTEKHENERGO

Moscow 1990

DEVELOPED State Order of the Red Banner of Labor Scientific Research Energy Institute named after. G.M. Krzhizhanovsky

PERFORMERS M.N. EGAI, O.M. KORSHUNOV, A.S. LEONOVICH, V.V. NUSHTAYKIN, V.K. RYBALKO, B.V. TARNIZHEVSKY, V.G. BULYCHEV

APPROVED Main Scientific and Technical Directorate of Energy and Electrification 12/07/89

Head V.I. GORY

Validity period is set

from 01.01.90

until 01.01.92

These Guidelines establish the procedure for performing calculations and contain recommendations for the design of solar heating systems for residential, public and industrial buildings and structures.

The guidelines are intended for designers and engineers involved in the development of solar heating and hot water supply systems.

. GENERAL PROVISIONS

where f - share of the total average annual heat load provided by solar energy;

where F - surface area of ​​the SC, m2.

where H is the average annual total solar radiation on a horizontal surface, kW h/m2 ; located from the application;

a, b - parameters determined from equation () and ()

where r - characteristics of the thermal insulation properties of the building envelope at a fixed value of the DHW load, is the ratio of the daily heating load at an outside air temperature of 0 °C to the daily DHW load. The more r , the greater the share of the heating load compared to the share of the DHW load and the less perfect the building design is in terms of heat losses; r = 0 is taken into account only DHW systems. The characteristic is determined by the formula

where λ is the specific heat loss of the building, W/(m 3 °C);

m - number of hours in a day;

k - ventilation air exchange rate, 1/day;

ρ in - air density at 0 °C, kg/m3;

f - replacement rate, approximately taken from 0.2 to 0.4.

Values ​​of λ, k, V, t in, s laid down when designing the SST.

Values ​​of coefficient α for solar collectors Types II and III

	Coefficient values
	α 1	α 2	α 3	α 4	α 5	α 6	α 7	α 8	α 9
	607,0	80,0		1340,0	437,5	22,5	1900,0	1125,0	25,0
	298,0	148,5	61,5	150,0	1112,0	337,5	700,0	1725,0	775,0

β coefficient values ​​for solar collectors Types II and III

	Coefficient values
	β 1	β 2	β 3	β 4	β 5	β 6	β 7	β 8	β 9
	1,177	0,496	0,140			0,995	3,350	5,05	1,400
	1,062	0,434	0,158	2,465	2,958	1,088	3,550	4,475	1,775

Values ​​of coefficients a and bare from the table. .

The values ​​of the coefficients a and b depending on the type of solar collector

	Coefficient values
		0,75
		0,80

where qi - specific annual heating capacity of SGVS at values f different from 0.5;

Δq - change in the annual specific heat output of the SGVS, %.

Change in annual specific heat outputΔq from the annual intake of solar radiation on a horizontal surface H and coefficient f

. RECOMMENDATIONS FOR DESIGNING SOLAR HEATING SYSTEMS where З с - specific reduced costs per unit of generated thermal energy SST, rub./GJ; Zb - specific reduced costs per unit of thermal energy generated by the basic installation, rub./GJ. where C c - reduced costs for SST and backup, rub./year; where k c - capital costs for SST, rub.; k in - capital costs for the backup, rub.; E n - standard coefficient of comparative efficiency of capital investments (0.1); E s is the share of operating costs from capital costs for the STS; E in - the share of operating costs from the capital costs of the backup; C is the cost of a unit of thermal energy generated by the backup, rub./GJ; N d - the amount of thermal energy generated by the backup during the year, GJ; k e - effect from reducing environmental pollution, rub.; k n - social effect from saving the salaries of personnel servicing the backup, rub. Specific reduced costs are determined by the formula where C b - reduced costs for a basic installation, rub./year;	Definition of the term
	solar collector	A device for capturing solar radiation and converting it into thermal and other types of energy
Hourly (daily, monthly, etc.) heating output	The amount of thermal energy removed from the collector per hour (day, month, etc.) of operation
Flat solar collector	Non-focusing solar collector with an absorbing element of a flat configuration (such as “pipe in sheet”, only from pipes, etc.) and flat transparent insulation
Heat-receiving surface area	Surface area of ​​the absorbing element illuminated by the sun under conditions of normal incidence of rays
Heat loss coefficient through transparent insulation (bottom, side walls of the collector)	Heat flow into the environment through transparent insulation (bottom, side walls of the collector), per unit area of ​​the heat-receiving surface, with a difference in the average temperatures of the absorbing element and the outside air of 1 ° C
Specific coolant flow in a flat solar collector	Coolant flow in the collector per unit area of ​​the heat-receiving surface
Efficiency factor	A value characterizing the efficiency of heat transfer from the surface of the absorbing element to the coolant and equal to the ratio of the actual heat output to the heat output, provided that all thermal resistances of heat transfer from the surface of the absorbing element to the coolant are zero
Surface blackness degree	Ratio of surface radiation intensity to black body radiation intensity at the same temperature
Glazing transmittance	The fraction of solar (infrared, visible) radiation incident on the surface of the transparent insulation transmitted by transparent insulation
Understudy	A traditional source of thermal energy that provides partial or complete coverage of the thermal load and works in combination with a solar heating system
Solar Thermal System	A system that covers heating and hot water loads using solar energy

Appendix 2

Thermal characteristics of solar collectors

	Collector type
Total heat loss coefficient U L, W/(m 2 °C)
Absorption capacity of the heat-receiving surface α	0,95	0,90	0,95
The degree of emissivity of the absorption surface in the range of operating temperatures of the collector ε	0,95	0,10	0,95
Glazing transmittance τ p	0,87	0,87	0,72
Efficiency factor F R	0,91	0,93	0,95
Maximum coolant temperature, °C
Note. I - single-glass non-selective collector; II - single-glass selective collector; III - double-glass non-selective collector.

Appendix 3

Technical characteristics of solar collectors

	Manufacturer
	Bratsk Heating Equipment Plant	Spetsgelioteplomontazh GSSR	KievZNIIEP	Bukhara solar equipment plant
Length, mm	1530	1000 - 3000	1624	1100
Width, mm			1008
Height, mm		70 - 100
Weight, kg	50,5	30 - 50
Heat-receiving surface, m		0,6 - 1,5		0,62
Operating pressure, MPa		0,2 - 0,6

Appendix 4

Technical characteristics of flow-through heat exchangers type TT

	Outer/inner diameter, mm		Flow area		Heating surface of one section, m 2	Section length, mm	Weight of one section, kg
			inner pipe, cm 2	annular channel, cm 2
	inner pipe	outer pipe
TT 1-25/38-10/10	25/20	38/32	3,14	1,13		1500
TT 2-25/38-10/10	25/20	38/32	6,28	6,26		1500

Appendix 5

Annual arrival of total solar radiation on a horizontal surface (N), kW h/m 2

Azerbaijan SSR
Baku	1378
Kirovobad	1426
Mingachevir	1426
Armenian SSR
Yerevan	1701
Leninakan	1681
Sevan	1732
Nakhchivan	1783
Georgian SSR
Telavi	1498
Tbilisi	1396
Tskhakaya	1365
Kazakh SSR
Almaty	1447
Guryev	1569
Fort Shevchenko	1437
Dzhezkazgan	1508
Ak-Kum	1773
Aral Sea	1630
Birsa-Kelmes	1569
Kustanay	1212
Semipalatinsk	1437
Dzhanybek	1304
Kolmykovo	1406
Kirghiz SSR
Frunze	1538
Tien Shan	1915
RSFSR
Altai region
Blagoveshchenka	1284
Astrakhan region
Astrakhan	1365
Volgograd region
Volgograd	1314
Voronezh region
Voronezh	1039
Stone steppe	1111
Krasnodar region
Sochi	1365
Kuibyshev region
Kuibyshev	1172
Kursk region
Kursk	1029
Moldavian SSR
Kishinev	1304
Orenburg region
Buzuluk	1162
Rostov region
Tsimlyansk	1284
Giant	1314
Saratov region
Ershov	1263
Saratov	1233
Stavropol region
Essentuki	1294
Uzbek SSR
Samarkand	1661
Tamdybulak	1752
Takhnatash	1681
Tashkent	1559
Termez	1844
Fergana	1671
Churuk	1610
Tajik SSR
Dushanbe	1752
Turkmen SSR
Ak-Molla	1834
Ashgabat	1722
Hasan-Kuli	1783
Kara-Bogaz-Gol	1671
Chardzhou	1885
Ukrainian SSR
Kherson region
Kherson	1335
Askania Nova	1335
Sumy region
Konotop	1080
Poltava region
Poltava	1100
Volyn region
Kovel	1070
Donetsk region
Donetsk	1233
Transcarpathian region
Beregovo	1202
Kyiv region
Kyiv	1141
Kirovograd region
Znamenka	1161
Crimean region
Evpatoria	1386
Karadag	1426
Odessa region
	30,8	39,2	49,8	61,7	70,8	75,3	73,6	66,2	55,1	43,6	33,6	28,7
	28,8	37,2	47,8	59,7	68,8	73,3	71,6	64,2	53,1	41,6	31,6	26,7
	26,8	35,2	45,8	57,7	66,8	71,3	69,6	62,2	51,1	39,6	29,6	24,7
	24,8	33,2	43,8	55,7	64,8	69,3	67,5	60,2	49,1	37,6	27,6	22,7
	22,8	31,2	41,8	53,7	62,8	67,3	65,6	58,2	47,1	35,6	25,6	20,7
	20,8	29,2	39,8	51,7	60,8	65,3	63,6	56,2	45,1	33,6	23,6	18,7
	18,8	27,2	37,8	49,7	58,8	63,3	61,6	54,2	43,1	31,6	21,6	16,7
	16,8	25,2	35,8	47,7	56,8	61,3
Boiling point, °C	106,0	110,0	107,5	105,0	113,0
Viscosity, 10 -3 Pa s:
at a temperature of 5 °C		5,15		6,38
at a temperature of 20 °C					7,65
at a temperature of -40 °C	7,75	35,3		28,45
Density, kg/m 3				1077	1483 - 1490
Heat capacity kJ/(m 3 °C):
at a temperature of 5 °C	3900	3524
at a temperature of 20 °C				3340	3486
Corrosivity	Strong	Average	Weak	Weak	Strong
Toxicity	No	Average	No	Weak	No

Notes e. Coolants based on potassium carbonate have the following compositions (mass fraction):

Recipe 1 Recipe 2

Potassium carbonate, 1.5-water 51.6 42.9

Sodium phosphate, 12-hydrate 4.3 3.57

Sodium silicate, 9-hydrate 2.6 2.16

Sodium tetraborate, 10-hydrate 2.0 1.66

Fluoreszoin 0.01 0.01

Water Up to 100 Up to 100

Building solar heating for a private house with your own hands is not difficult task, as it seems to the ignorant layman. This will require welding skills and materials available at any hardware store.

The relevance of creating solar heating for a private house with your own hands

Gaining complete autonomy is the dream of every owner who starts private construction. But is solar energy really capable of heating a residential building, especially if the device for storing it is assembled in the garage?

Depending on the region, the solar flux can range from 50 W/sq.m on a cloudy day to 1400 W/sq.m with a clear summer sky. With such indicators, even a primitive collector with low efficiency (45-50%) and an area of ​​15 sq.m. can produce about 7000-10000 kWh per year. And this is 3 tons of firewood saved for a solid fuel boiler!

• on average, there are 900 W per square meter of device;
• to increase the water temperature, it is necessary to spend 1.16 W;
• taking into account also the heat loss of the collector, 1 sq.m can heat about 10 liters of water per hour to a temperature of 70 degrees;
• to provide 50 liters of hot water needed by one person, you will need to spend 3.48 kW;
• after checking the hydrometeorological center data on power solar radiation(W/sq.m) in the region, it is necessary to divide 3480 W by the resulting solar radiation power - this will be the required area of ​​the solar collector to heat 50 liters of water.

As it becomes clear, effective autonomous heating exclusively using solar energy is quite problematic. After all, during the gloomy winter season there is very little solar radiation, and it is impossible to place a collector with an area of ​​120 sq.m. on the site. it won't always work out.

So are solar collectors really non-functional? Don't discount them in advance. So, with the help of such a storage device you can do without a boiler in the summer - the power will be enough to provide for your family hot water. In winter, it will be possible to reduce energy costs if you supply already heated water from the solar collector to an electric boiler.
In addition, the solar collector will be an excellent assistant to the heat pump in a house with low-temperature heating (warm floors).

So, in winter, the heated coolant will be used in heated floors, and in summer, excess heat can be sent to the geothermal circuit. This will reduce the power of the heat pump.
After all geothermal heat is not renewed, so that over time an ever-increasing “cold bag” forms in the soil thickness. For example, in a conventional geothermal circuit at the beginning heating season the temperature is +5 degrees, and at the end -2C. When heated, the initial temperature rises to +15 C, and by the end of the heating season does not fall below +2 C.

Construction of a homemade solar collector

For a master who is confident in his abilities, assembling a heat collector will not be difficult. You can start with a small device to provide hot water in your dacha, and if the experiment is successful, move on to creating a full-fledged solar station.

Flat-plate solar collector made of metal pipes

The simplest collector to make is a flat one. For its device you will need:

• welding machine;
• pipes from of stainless steel or copper;
• steel sheet;
• tempered glass or polycarbonate;
• wooden boards for the frame;
• non-flammable insulation that can withstand metal heated to 200 degrees;
• black matte paint resistant to high temperatures.

Assembly of the solar collector is quite simple:

1. Pipes are welded to steel sheet– it acts as an adsorber of solar energy, so the fit of the pipes should be as tight as possible. Everything is painted matte black.



2. A frame is placed on the sheet with pipes so that the pipes are facing inside. Holes are drilled for the inlet and outlet of the pipes. Insulation is being installed. If a hygroscopic material is used, you need to take care of waterproofing - after all, once wet, the insulation will no longer protect the pipes from cooling.





3. The insulation is fixed with an OSB sheet, all joints are filled with sealant.
4. On the adsorber side, transparent glass or polycarbonate with a small air gap is placed. It serves to prevent the steel sheet from cooling.
5. You can fix the glass using wooden window beads, after applying sealant. It will prevent cold air from entering and protect the glass from shrinking the frame when heating and cooling.

For the collector to function fully, you will need a storage tank. It can be made from a plastic barrel, insulated on the outside, in which a heat exchanger connected to a solar collector is laid in a spiral. The heated water inlet should be located at the top, and the cold water outlet at the bottom.

It is important to place the tank and manifold correctly. To ensure natural circulation of water, the tank must be located above the collector, and the pipes must have a constant slope.

Solar heater made from scrap materials

If with welding machine It was not possible to establish a friendship, you can make a simple solar heater from what is at hand. For example, from tin cans. To do this, holes are made in the bottom, the cans themselves are fastened to each other with sealant, and they are seated on it at the junction with PVC pipes. They are painted black and placed in a frame under glass in the same way as ordinary pipes.

Solar house facade

Why not decorate the house with something useful instead of ordinary siding? For example, by making a solar heater on the entire wall on the south side.

This solution will allow optimizing heating costs in two directions at once - reducing energy costs and significantly reducing heat loss due to additional insulation facade.

The device is incredibly simple and does not require special tools:

• a painted galvanized sheet is laid on the insulation;
• stainless steel is laid on top corrugated pipe, also painted black;
• everything is covered with polycarbonate sheets and fixed with aluminum corners.

If this method seems complicated, the video shows a version made from tin, polypropylene pipes and films. Much easier!

Classification and main elements of solar systems

Solar heating systems are systems that use solar radiation as a source of thermal energy. Their characteristic difference from other systems is low temperature heating is the use of a special element - a solar receiver, designed to capture solar radiation and convert it into thermal energy.

According to the method of using solar radiation, solar low-temperature heating systems are divided into passive and active.

Passive solar heating systems are those in which the building itself or its individual enclosures (building-collector, wall-collector, roof-collector, etc.) serve as an element that receives solar radiation and converts it into heat (Fig. 3.4)) .

Rice. 3.4. Passive low-temperature solar heating system “wall-collector”: 1 – solar rays; 2 – translucent screen; 3 – air damper; 4 – heated air; 5 – cooled air from the room; 6 – own long-wave thermal radiation of the wall mass; 7 – black beam-receiving surface of the wall; 8 – blinds.

Active are solar low-temperature heating systems in which the solar receiver is an independent separate device not related to the building. Active solar systems can be subdivided:

- by purpose (hot water supply, heating systems, combined systems for heat and cold supply purposes);

- by type of coolant used (liquid - water, antifreeze and air);

- by duration of work (year-round, seasonal);

- By technical solution circuits (one-, two-, multi-circuit).

Air is a widely used coolant that does not freeze over the entire range of operating parameters. When using it as a coolant, it is possible to combine heating systems with a ventilation system. However, air is a low-heat-capacity coolant, which leads to an increase in metal consumption for the installation of air heating systems compared to water systems.

Water is a heat-intensive and widely available coolant. However, at temperatures below 0°C, it is necessary to add antifreeze liquids to it. In addition, it must be taken into account that water saturated with oxygen causes corrosion of pipelines and equipment. But the metal consumption in solar water systems is much lower, which greatly contributes to their wider use.

Seasonal solar hot water supply systems are usually single-circuit and operate in the summer and transition months, during periods with positive outside temperatures. They can have an additional heat source or do without it, depending on the purpose of the serviced object and operating conditions.

Solar heating systems for buildings are usually double-circuit or, most often, multi-circuit, and different coolants can be used for different circuits (for example, in the solar circuit - aqueous solutions of non-freezing liquids, in the intermediate circuits - water, and in the consumer circuit - air).

Combined year-round solar systems for the purposes of heat and cold supply to buildings are multi-circuit and include an additional heat source in the form of a traditional heat generator running on fossil fuels or a heat transformer.

Schematic diagram solar heating system is shown in Fig. 3.5. It includes three circulation circuits:

- the first circuit, consisting of solar collectors 1, circulation pump 8 and liquid heat exchanger 3;

- the second circuit, consisting of a storage tank 2, a circulation pump 8 and a heat exchanger 3;

- the third circuit, consisting of a storage tank 2, a circulation pump 8, a water-air heat exchanger (heater) 5.

Rice. 3.5. Schematic diagram of the solar heating system: 1 – solar collector; 2 – storage tank; 3 – heat exchanger; 4 – building; 5 – heater; 6 – heating system backup; 7 – hot water supply system backup; 8 - circulation pump; 9 – fan.

The solar heating system operates as follows. The coolant (antifreeze) of the heat receiving circuit, heating up in the solar collectors 1, enters the heat exchanger 3, where the heat of the antifreeze is transferred to the water circulating in the interpipe space of the heat exchanger 3 under the action of the pump 8 of the secondary circuit. The heated water enters the storage tank 2. From the storage tank, water is taken by the hot water supply pump 8, brought, if necessary, to the required temperature in the backup 7 and enters the hot water supply system of the building. The storage tank is recharged from the water supply.

For heating, water from the storage tank 2 is supplied by the third circuit pump 8 to the heater 5, through which air is passed through with the help of a fan 9 and, when heated, enters the building 4. In the absence of solar radiation or lack of thermal energy generated by solar collectors, the backup 6 is turned on.

The selection and arrangement of elements of a solar heating system in each specific case are determined by climatic factors, purpose of the facility, heat consumption regime, and economic indicators.

Concentrating solar receivers

Concentrating solar receivers are spherical or parabolic mirrors (Fig. 3.6), made of polished metal, at the focus of which a heat-receiving element (solar boiler) is placed, through which the coolant circulates. Water or non-freezing liquids are used as a coolant. When using water as a coolant at night and during cold periods, the system must be emptied to prevent it from freezing.

To ensure high efficiency of the process of capturing and converting solar radiation, the concentrating solar receiver must be constantly directed strictly at the Sun. For this purpose, the solar receiver is equipped with a tracking system, including a direction sensor to the Sun, an electronic signal conversion unit, and an electric motor with a gearbox for rotating the solar receiver structure in two planes.

The advantage of systems with concentrating solar receivers is the ability to generate heat at a relatively high temperature (up to 100 °C) and even steam. The disadvantages include the high cost of the structure; the need to constantly clean reflective surfaces from dust; work only during daylight hours, and therefore the need for large batteries; large energy costs for driving the solar tracking system, commensurate with the energy generated. These disadvantages hinder the widespread use of active low-temperature solar heating systems with concentrating solar receivers. Recently, flat solar receivers have been most often used for solar low-temperature heating systems.

Flat-plate solar collectors

Flat solar collector is a device with a flat configuration absorbing panel and flat transparent insulation for absorbing solar radiation energy and converting it into heat.

Flat-plate solar collectors (Fig. 3.7) consist of a glass or plastic cover (single, double, triple), a heat-receiving panel painted black on the side facing the sun, insulation on the reverse side and a housing (metal, plastic, glass, wooden).

Any metal or plastic sheet with channels for coolant can be used as a heat-receiving panel. Heat-receiving panels are made of aluminum or steel of two types: sheet-pipe and stamped panels (pipe in sheet). Plastic panels due to their fragility and rapid aging under influence sun rays, and also due to low thermal conductivity, are not widely used.

Rice. 3.6 Concentrating solar receivers: a – parabolic concentrator; b – parabolic cylindrical concentrator; 1 – sun rays; 2 – heat-receiving element (solar collector); 3 – mirror; 4 – tracking system drive mechanism; 5 – pipelines supplying and discharging coolant.

Rice. 3.7. Flat solar collector: 1 – sun rays; 2 – glazing; 3 – body; 4 – heat-receiving surface; 5 – thermal insulation; 6 – seal; 7 – own long-wave radiation of the heat-receiving plate.

Under the influence of solar radiation, heat-receiving panels heat up to temperatures of 70-80 ° C, exceeding the ambient temperature, which leads to an increase in the convective heat transfer of the panel to the environment and its own radiation to the sky. To achieve higher coolant temperatures, the surface of the plate is covered with spectral-selective layers that actively absorb short-wave radiation from the sun and reduce its own thermal radiation in the long-wave part of the spectrum. Such designs based on “black nickel”, “black chrome”, copper oxide on aluminum, copper oxide on copper and others are expensive (their cost is often comparable to the cost of the heat-receiving panel itself). Another way to improve the performance of flat plate collectors is to create a vacuum between the heat-receiving panel and the transparent insulation to reduce heat loss (fourth generation solar collectors).

Experience in operating solar installations based on solar collectors has revealed a number of significant disadvantages of such systems. First of all, this is the high cost of collectors. Increasing the efficiency of their operation through selective coatings, increasing the transparency of glazing, evacuation, as well as installing a cooling system turn out to be economically unprofitable. A significant disadvantage is the need to frequently clean the glass from dust, which practically excludes the use of the collector in industrial areas. During long-term operation of solar collectors, especially in winter conditions, their frequent failure is observed due to the uneven expansion of illuminated and darkened areas of glass due to the violation of the integrity of the glazing. There is also a large percentage of collectors failing during transportation and installation. A significant disadvantage of operating systems with collectors is also the uneven loading throughout the year and day. Experience in operating collectors in Europe and the European part of Russia with a high proportion of diffuse radiation (up to 50%) has shown the impossibility of creating a year-round autonomous hot water supply and heating system. All solar systems with solar collectors in mid-latitudes require the installation of large-volume storage tanks and the inclusion of an additional energy source in the system, which reduces the economic effect of their use. In this regard, it is most advisable to use them in areas with high average intensity of solar radiation (not lower than 300 W/m2).

Description:

Of particular importance when designing Olympic venues in Sochi is the use of environmentally friendly renewable energy sources and, first of all, solar radiation energy. In this regard, the experience of developing and implementing passive solar systems heating supply in residential and public buildings in Liaoning Province (China), because geographical location and the climatic conditions of this part of China are comparable to those of Sochi.

Experience of the People's Republic of China

Zhao Jinling, Ph.D. tech. Sciences, Dalian Polytechnic University (PRC), intern at the Department of Industrial Thermal Power Systems,

A. Ya. Shelginsky, Doctor of Technical Sciences sciences, prof., scientific. Head, MPEI (TU), Moscow

Of particular importance when designing Olympic venues in Sochi is the use of environmentally friendly renewable energy sources and, first of all, solar radiation energy. In this regard, the experience of developing and implementing passive solar heating systems in residential and public buildings in Liaoning Province (China) will be of interest, since the geographical location and climatic conditions of this part of China are comparable to those of Sochi.

The use of renewable energy sources (RES) for heat supply systems is relevant and very promising at present, subject to a competent approach to this issue, since traditional energy sources (oil, gas, etc.) are not unlimited. In this regard, many countries, including China, are switching to the use of environmentally friendly renewable energy sources, one of which is the heat of solar radiation.

Opportunity effective use solar radiation heat in the People's Republic of China depends on the region, since the climatic conditions in different parts countries are very different: from temperate continental (west and north) with hot summers and harsh winters, subtropical in the central regions of the country to tropical monsoon on the southern coast and islands, determined by the geographical location of the territory where the object is located (table).

Table Distribution of solar resources across China

Zone Annual duration insolation, h Solar radiation, MJ/(m 2 .year) Area China Relevant areas in other countries of the world I 2 800-3 300 7 550-9 250 Tibet, etc. Northern regions of Pakistan and India II 3 000-3 200 5 850-7 550 Hebei, etc. Jakarta (Indonesia) III 2 200-3 000 5 000-5 850 Beijing, Dalian, etc. Washington (USA) IV 1 400-2 200 4 150-5 000 Hubzhi, Hunan, etc. Milan (Italy), Germany, Japan V 1 000-1 400 3 350-4 150 Sichuan and Guizhou Paris (France), Moscow (Russia)

In Liaoning province, the intensity of solar radiation ranges from 5,000 to 5,850 MJ/m2 per year (in Sochi - about 5,000 MJ/m2 per year), which makes it possible to actively use heating and cooling systems for buildings based on the use of solar radiation energy. Such systems that convert the heat of solar radiation and outside air can be divided into active and passive.

Passive solar heating systems (PSHS) use the natural circulation of heated air (Fig. 1), i.e., gravitational forces.

Active solar thermal systems (Fig. 2) use additional energy sources to ensure its operation (for example, electricity). The heat of solar radiation enters solar collectors, where it is partially accumulated and transferred to an intermediate coolant, which is transported and distributed throughout the premises by pumps.

Systems with zero heat and cold consumption are possible, where the appropriate indoor air parameters are provided without additional energy consumption due to:

• necessary thermal insulation;
• selection of building construction materials with appropriate heat and cold storage properties;
• use in the system of additional heat and cold accumulators with appropriate characteristics.

In Fig. 3 shows an improved operating diagram passive system heating supply of the building with elements (curtains, valves) that allow more precise regulation of the indoor air temperature. On the south side of the building, a so-called Trombe wall is installed, which consists of a massive wall (concrete, brick or stone) and a glass partition installed at a short distance from the wall with outside. The outer surface of the massive wall is painted in dark color. Through the glass partition, the massive wall and the air located between the glass partition and the massive wall are heated. A heated massive wall, due to radiation and convective heat exchange, transfers the accumulated heat into the room. Thus, this design combines the functions of a collector and a heat accumulator.

The air located in the layer between the glass partition and the wall is used as a coolant to supply heat to the room during cold periods and on sunny days. To prevent heat outflows into the environment during the cold period at night and excess heat inflows on sunny days during the warm period, curtains are used, which significantly reduce the heat exchange between the solid wall and the external environment.

Curtains are made from nonwovens with silver coating. To ensure the necessary air circulation, air valves are used, which are located in the upper and lower parts of the solid wall. Automatic control of the operation of air valves allows you to maintain the necessary heat inflows or heat outflows in the serviced room.

A passive solar heating system works as follows:

1. During cold periods (heating):

• sunny day - the curtain is raised, valves are open(Fig. 3a). This leads to heating of the massive wall through the glass partition and heating of the air located in the layer between the glass partition and the wall. Heat enters the room from the heated wall and the air heated in the interlayer, circulating through the interlayer and the room under the influence of gravitational forces caused by the difference in air densities at different temperatures (natural circulation);
• night, evening or cloudy day - the curtain is lowered, the valves are closed (Fig. 3b). Heat outflows in external environment are significantly reduced. The temperature in the room is maintained by the flow of heat from a massive wall that has accumulated this heat from solar radiation;

2. During the warm period of time (cooling):

• sunny day - the curtain is lowered, the lower valves are open, the upper ones are closed (Fig. 3c). The curtain protects the massive wall from heating from solar radiation. Outside air enters the room from the shaded side of the house and exits through the layer between the glass partition and the wall into the environment;
• night, evening or cloudy day - the curtain is raised, the lower valves are open, the upper ones are closed (Fig. 3d). Outside air enters the room from the opposite side of the house and exits into the environment through the layer between the glass partition and the solid wall. The wall is cooled as a result of convective heat exchange with air passing through the layer, and due to the outflow of heat by radiation into the environment. The cooled wall maintains the required temperature in the room during the day.

To calculate passive solar heating systems for buildings, mathematical models of non-stationary heat transfer during natural convection have been developed to provide rooms with the necessary temperature conditions depending on the thermophysical properties of enclosing structures, daily changes in solar radiation and outside air temperature.

To determine the reliability and clarify the results obtained, an experimental model of a residential building located in Dalian with passive solar heating systems was developed, manufactured and studied at Dalian Polytechnic University. The Trombe Wall is located only on the southern façade, with automatic air valves and curtains (Fig. 3, photo).

When conducting the experiment we used:

• small weather station;
• instruments for measuring the intensity of solar radiation;
• anemograph RHAT-301 for determining indoor air speed;
• TR72-S thermometer and thermocouples for measuring room temperature.

Experimental studies were carried out in the warm, transitional and cold periods of the year under various meteorological conditions.

The algorithm for solving the problem is presented in Fig. 4.

The experimental results confirmed the reliability of the obtained calculated relationships and made it possible to correct individual dependencies taking into account specific boundary conditions.

Currently, there are many residential buildings and schools in Liaoning Province that use passive solar heating systems.

An analysis of passive solar heat supply systems shows that they are quite promising in certain climatic regions in comparison with other systems for the following reasons:

• cheapness;
• ease of maintenance;
• reliability.

The disadvantages of passive solar heating systems include the fact that indoor air parameters may differ from the required (calculated) ones when the outside air temperature changes beyond the limits accepted in the calculations.

To achieve a good energy-saving effect in heating and cooling systems for buildings with more accurate maintenance of temperature conditions within specified limits, it is advisable to combine passive and active solar heating and cooling systems.

In this regard, further theoretical research and experimental work on physical models taking into account previously obtained results.

Literature

1. Zhao Jinling, Chen Bin, Liu Jingjun, Wang Yongxun Dynamic thermal performance simulation of an improved passive solar house with trombe wall ISES Solar word Congress, 2007, Beijing China, Vols 1-V: 2234–2237.

2. Zhao Jinling, Chen Bin, Chen Cuiying, Sun Yuanyuan Study on dynamic thermal response of the passive solar heating systems. Journal of Harbin Institute of Technology (New Series). 2007. Vol. 14: 352–355.

With rising energy prices, the use of alternative sources energy. And since heating is the main expense item for many, we are talking about heating first of all: you have to pay practically all year round and considerable amounts. When you want to save money, the first thing that comes to mind is solar heat: a powerful and completely free source of energy. And it’s quite possible to use it. Moreover, although the equipment is expensive, it is several times cheaper than heat pumps. Let's talk in more detail about how solar energy can be used to heat a house.

Solar heating: pros and cons

If we talk about using solar energy for heating, we need to keep in mind that there are two different devices to convert solar energy:

Both options have their own characteristics. Although it must be said right away, whichever one you choose, do not rush to abandon the heating system that you have. The sun rises, of course, every morning, but not always on your Solar cells There will be enough light coming in. The most reasonable solution is to make a combined system. When the sun's energy is sufficient, the second heat source will not work. This way you will protect yourself, live in comfortable conditions, and save money.

If there is no desire or opportunity to install two systems, your solar heating should have at least a double power reserve. Then we can say for sure that you will have warmth in any case.

Advantages of using solar energy for heating:

Flaws:

• Dependence of the amount of incoming heat on the weather and region.
• For guaranteed heating, you will need a system that can operate in parallel with a solar heating system. Many heating equipment manufacturers provide this possibility. In particular, European manufacturers of wall-mounted gas boilers provide for joint operation with solar heating (for example, Baxi boilers). Even if you have installed equipment that does not have this capability, you can coordinate the work heating system using a controller.
• Solid financial investment at the start.
• Periodic maintenance: tubes and panels must be cleaned of adhering debris and washed from dust.
• Some of the liquid solar collectors cannot operate under very low temperatures Oh. On the eve of severe frosts, the liquid must be drained. But this does not apply to all models and not all liquids.

Now let's take a closer look at each type of solar heating element.

Solar collectors

Solar collectors are used for solar heating. These installations use the heat of the sun to heat the coolant fluid, which can then be used in a water heating system. The specificity is that a solar water heater for heating a house produces only a temperature of 45-60 o C, and shows the highest efficiency at 35 o C at the outlet. Therefore, such systems are recommended for use in conjunction with warm water floors. If you don’t want to give up radiators, either increase the number of sections (approximately twice as much) or heat up the coolant.

To provide a home warm water and for water heating you can use solar collectors (flat and tubular)

Now about the types of solar collectors. Structurally there are two modifications:

• flat;
• tubular.

In each of the groups there are variations in both materials and design, but they have the same operating principle: a coolant runs through the tubes, which is heated by the sun. But the designs are completely different.

Flat-plate solar collectors

These solar heating units have a simple design and therefore can be made with your own hands if desired. A durable bottom is secured to a metal frame. A layer of thermal insulation is laid on top. The housing walls are also insulated to reduce losses. Then there is a layer of adsorber - a material that absorbs solar radiation well, turning it into heat. This layer is usually black in color. The adsorber is equipped with pipes through which the coolant flows. From above, this entire structure is closed with a transparent lid. The material for the cover can be tempered glass or one of the plastics (most often it is polycarbonate). In some models, the light-transmitting material of the cover may undergo special treatment: to reduce reflectivity, it is made not smooth, but slightly matte.

The pipes in a flat-plate solar collector are usually laid in a snake pattern, and there are two holes - inlet and outlet. Single-pipe and two-pipe connection. This is what you like. But for normal heat exchange a pump is needed. A gravity-flow system is also possible, but it will be very inefficient due to the low speed of the coolant. It is this type of solar collector that is used for heating, although it can be used to efficiently heat water for hot water supply.

There is a variant of a gravity collector, but it is used mainly for heating water. This design is also called a plastic solar collector. These are two plates of transparent plastic, hermetically sealed to the body. There is a labyrinth inside to move water. Sometimes the bottom panel is painted black. There are two holes - inlet and outlet. Water is supplied inside, warmed by the sun as it moves through the labyrinth, and comes out warm. This scheme works well with a water tank and easily heats water for domestic hot water. This is a modern replacement for a conventional barrel mounted on summer shower. Moreover, a more effective replacement.

How efficient are solar collectors? Among all domestic solar systems today they show top scores: their efficiency is 72-75%. But not everything is so good:

• they do not work at night and do not work well in cloudy weather;
• large heat losses, especially in windy conditions;
• low maintainability: if something breaks down, then a significant part, or the entire panel, needs to be replaced.

However, heating a private house from the sun is often done using these solar installations. Such installations are popular in southern countries with active radiation and positive temperatures in winter period. They are not suitable for our winters, but in the summer season they show good results.

Air manifold

This installation can be used for air heating of the house. Structurally, it is very similar to the plastic collector described above, but air circulates and heats up in it. Such devices are hung on walls. They can operate in two ways: if the solar air heater is sealed, air is taken from the room, heated and returned to the same room.

There is another option. It combines heating with ventilation. There are holes in the outer housing of the air manifold. Through them, cold air enters the structure. Passing through the labyrinth, it is heated by the sun's rays, and then warmed up it enters the room.

Such heating of the house will be more or less effective if the installation occupies the entire southern wall, and there is no shadow on this wall.

Tubular manifolds

Here, too, the coolant circulates through pipes, but each of these heat exchange pipes is inserted into a glass flask. They are all connected in a manifold, which is essentially a comb.

Diagram of a tubular collector (click to enlarge the picture)

Tubular collectors have two types of tubes: coaxial and feather. Coaxial - a pipe in a pipe - nested one inside the other and their edges are sealed. A rarefied airless environment is created inside between the two walls. That is why such tubes are also called vacuum tubes. Feather tubes are just a regular tube sealed on one side. And they are called feather ones because, to increase heat transfer, an adsorber plate is inserted into them, which has curved edges and is somewhat reminiscent of a feather.

In addition, heat exchangers can be inserted into different housings different types. The first are the Heat-pipe thermal channels. This is a whole system for converting sunlight into thermal energy. A heat-pipe is a small-diameter hollow copper tube sealed at one end. On the second there is a massive tip. A substance with a low boiling point is poured into the tube. When heated, the substance begins to boil, part of it goes into gaseous state and rises up the tube. Along the way from the heated walls of the tube, it heats up more and more. It ends up in the upper part, where it stays for some time. During this time, the gas transfers part of the heat to the massive tip, gradually cools, condenses and settles down, where the process is repeated again.

The second method is U-type, which is a traditional tube filled with coolant. There's no news or surprises here. Everything is as usual: the coolant enters on one side, passes through the tube, and is heated by sunlight. Despite its simplicity, this type of heat exchanger is more efficient. But it is used less often. And all because solar water heaters of this type form a single whole. If one tube is damaged, the entire section must be replaced.

Tubular collectors with a Heat-pipe system are more expensive, show lower efficiency, but are used more often. And all because a damaged tube can be changed in a couple of minutes. Moreover, if a coaxial flask is used, then the tube can also be repaired. It is simply disassembled (the top plug is removed) and the damaged element (thermal channel or the bulb itself) is replaced with a working one. The tube is then inserted into place.

Which collector is better for heating?

For southern regions with mild winters and big amount sunny days a year the best option- flat collector. In such a climate it shows the highest productivity.

For regions with harsher climates, tubular collectors are suitable. Moreover, systems with Heat-pipe are more suitable for harsh winters: they heat even at night and even in cloudy weather, collecting most of the solar radiation spectrum. They are not afraid of low temperatures, but the exact temperature range needs to be clarified: it depends on the substance located in the thermal channel.

These systems, when properly calculated, can be basic, but more often they simply save heating costs from another, paid source of energy.

Another auxiliary heating could be an air manifold. It can be made to cover the entire wall, and it can be easily done with your own hands. It is perfect for heating a garage or cottage. Moreover, problems with insufficient heating may arise not in winter, as you expect, but in autumn. In frost and snow, the sun's energy is many times greater than in cloudy, rainy weather.

Solar panels

When we hear the words “solar energy,” we first think of batteries that convert light into electricity. And this is done by special photoelectric converters. They are produced by industry from various semiconductors. Most often for household use We use silicon photocells. They have the most low price and show quite decent performance: 20-25%.

Solar panels for a private home are common in some countries

Solar panels can be used directly for heating only if the boiler or other heating device on electricity you connect to this current source. Also, solar panels in combination with electric batteries can be integrated into the home’s electricity supply system and thus reduce monthly bills for used electricity. In principle, it is quite possible to fully meet the family’s needs from these installations. It just takes a lot of money and space. On average, you can get 120-150W per square meter of panel. So count how many squares of roof or local area should be occupied by such panels.

Features of solar heating

The feasibility of installing a solar heating system raises doubts among many. The main argument is that it is expensive and will never pay for itself. We have to agree that it is expensive: the prices for equipment are quite high. But no one is stopping you from starting small. For example, to evaluate the effectiveness and practicality of the idea of ​​making a similar installation yourself. The costs are minimal, and you will have a first-hand idea. Then you will decide whether to get involved with all this or not. Here's the thing: all the negative messages are from theorists. Not a single one was encountered from practitioners. There is an active search for ways to improve and alterations, but no one said that the idea is useless. This says something.

Now let's talk about the fact that installing a solar heating system will never pay off. While the term is paying off

There is a lot of bridges in our country. It is comparable to the service life of solar collectors or batteries. But if you look at the dynamics of price growth for all energy resources, you can assume that it will soon decrease to a completely acceptable time frame.

Now let's talk about how to make the system. First of all, you need to determine the needs of your home and family for heat and hot water. The general methodology for calculating a solar heating system is as follows:

• Knowing in which region the house is located, you can find out how much sunlight falls on 1m2 of area in each month of the year. Experts call this insolation. From this data, you can then estimate how many solar panels you need. But first you need to determine how much heat will be needed for DHW preparation and heating.
• If you have a hot water meter, then you know the volume of hot water you use monthly. Display the average consumption data for the month or calculate based on the maximum consumption - whoever wants it. You should also have data on heat losses at home.
• Take a look at the solar heaters you would like to install. Having data on their performance, you can roughly determine the number of elements needed to cover your needs.

In addition to determining the number of components of the solar system, you will need to determine the volume of the tank in which the solar energy will accumulate. hot water for DHW. This can be easily done if you know your family's actual expenses. If you have a DHW meter installed and you have data for several years, you can display the average consumption per day (divide the average consumption per month by the number of days). This is approximately the volume of tank you need. But the tank needs to be taken with a reserve of 20% or so. Just in case.

If there is no hot water supply or meter, you can use consumption standards. One person spends on average 100-150 liters of water per day. Knowing how many people permanently live in the house, you will calculate the required tank volume: the norm is multiplied by the number of residents.

It must be said right away that it is rational (from the point of view of payback) for middle zone Russia has a solar heating system that covers about 30% of heat demand and fully supplies hot water. This is an average result: in some months, heating will be 70-80% provided by the solar system, and in some months (December-January) only 10%. Again, a lot depends on the type solar panels and from the region of residence.

Moreover, it’s not just a matter of “to the north” or “to the south.” It's a matter of the number of sunny days. For example, in very cold Chukotka, solar heating will be very effective: the sun almost always shines there. In the much milder climate of England, with eternal fogs, its effectiveness is extremely low.
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Results

Despite many critics who talk about the inefficiency of solar energy and the long payback period, more and more people are at least partially switching to alternative sources. In addition to saving, many are attracted by independence from the state and its pricing policy. In order not to regret the wasted amounts of money invested, you can first conduct an experiment: make one of the solar installations with your own hands and decide for yourself how attractive it is to you (or not).