Within group of solar collectors without concentration are the vacuum tubes collectors.

Currently they are the most used.

As was seen in flat collector’s analysis, conversion of radiant energy from the sun to thermal energy leads to radiation, conduction and convection losses that progressively decrease the yield as temperature difference between collector and environment increases.

Improvement provided by vacuum tube collectors is to avoid conduction and convection losses.

If less heat is lost, we will in most cases obtain more yield for same amount of Sun energy.

We will see that this is not always the case and depends on temperature of use.

Vacuum collectors find their main application in intermediate temperature systems (heating, air conditioning, industrial processes, etc.) and in cold places with high differences between collector temperature and the environment.

The vacuum technique used by fluorescent tubes manufacturers has been developed and is the one used by vacuum tube manifolds manufacturers.

Vacuum tube collector systems are based on evacuated tubes.

These are formed by two concentric tubes between which the air has been sucked up producing a vacuum. At one end, both tubes are joined by sealing the vacuum. Inside both tubes are located the different types of absorbers that determine the different systems.

Single evacuated tubes are evacuated tubes, assembled directly with accumulation tank or independently, which may contain only water or water plus antifreeze.

A dark colored layer of absorbent material is located on evacuated tube inner wall.

When solar radiation strikes the absorbent material layer it is transformed into heat and raises the temperature of the fluid that is in contact with it.

The fluid is heated by convection and begins to rise through the tube being replaced by cold fluid which in turn heats up and restarts the process.

This type of vacuum tube offers the advantage of having the aforementioned few heat losses and the disadvantages of being very sensitive to pressure.

U-Pipe vacuum manifolds are used both in individual collectors and in compact solar systems with integrated tank.

Absorber can be placed on tube wall as in evacuated tube case or on an absorbent material sheet.

In any case, absorber is run on its surface by a pipe (preferably copper) through which the fluid raises its temperature in contact with it flows.

U-Pipe tube manifolds have the advantage of being able to adopt both horizontal and vertical position without impairing their performance since tube can rotate on its axis by tilting absorber in the most appropriate way in case the absorber has sheet shape.

Finally, in vacuum tube technology we find heat pipe manifolds.

They employ a mechanism consisting of a closed tube into which a vaporizing fluid (alcohol mixture) of specific properties is introduced.

When sun hits absorber attached to the tube, fluid evaporates and absorbs heat (latent heat). As gas rises above liquid to top of the tube where the cold spot is located. There it liquefies (condenses) and yields its latent heat to the fluid we are interested in heating by falling back to tube bottom by capillarity or gravity.

This process (evaporation – condensation) is repeated for sun’s radiation duration or until collector has reached a very high temperature (around 130 ° C or more).

They have the advantage that each tube is independent being able to change in full system operation. It is highly frost resistant.

Since tubes can also rotate on their axis, it is possible to adopt vertical and horizontal positions as in the case of U-Pipe systems, although in this case generally a minimum tube inclination (between 15º and 20º according to manufacturer) to allow fluid, once liquefied, to fall by gravity.

There are 3 qualities of these collectors:

– Dry union: heat exchange occurs without direct contact between heat transfer fluid and tube, which makes them very suitable in areas with unfavorable water qualities.

– Diode function: heat transfer is always carried out only in one direction, from absorber to heat transfer fluid, and never other way round.

– Temperature limitation: evaporation – condensation cycle takes place as long as vaporizing fluid critical temperature is not reached, thus avoiding uncontrolled temperature rise inside the tubes risks.

This content was extracted from the Solar Thermal Energy Technical-Commercial Manual and is part of Solar e-learning.

All you need is Sun. All you need is Sopelia.

Within the solar collectors without concentration we find the flat plate.

They were the most used, but have lost ground in favor of vacuum tube.

In flat collectors, the collector is located in a rectangular box (housing), whose usual dimensions are between 80 and 120 cm wide, 150 and 200 cm high, and 5 and 10 cm thick (although there are larger models).

The face exposed to the sun is covered by a very fine glass, while the remaining five faces are opaque and are thermally insulated.

Inside the box, on the face that is exposed to the sun, is placed a metal plate (absorber).

This plate is attached or welded to a series of conduits through which a heat transfer agent (usually water, glycol, or a mixture of both) flows.

A selective surface treatment is applied to mentioned plate or is simply black painted, to increase its heat absorption.

Flat solar collectors work taking advantage of greenhouse effect (the same principle that can be experienced when entering a car parked in the sun in summer).

After passing through the glass (transparent for wavelengths between 0.3 μm and 3 μm) radiation reaches absorber surface, which is heated and emits radiation with a wavelength between 4.5 μm 7.2 μm, for which the glass is opaque.

Approximately half of this last radiation diffuses to the outside, being lost; but the other half returns inward and thus contributes to absorber surface further heating.

As it passes through the box, the heat transfer fluid heats up and increases its temperature at absorber expense, which temperature will decrease.

The heat transfer fluid then transports that heat energy to where it is desired.

The flat solar collector is formed by 4 main elements:

1) Transparent cover: it must possess the necessary qualities (suitable transmission and thermal conductivity coefficients) to provoke the greenhouse effect and to losses reduce; ensuring manifold water and air sealing, in conjunction with housing and joints; do not keep outer surface dirt adhering so that rain easily slips.

2) Absorber: receives the solar radiation and converts it into heat that is transmitted to the heat transfer fluid.

Shapes are diverse: metal plates separated by a few millimeters, a metal plate with welded or embedded tubes or two metal plates with a circuit inside.

Face exposed to sun must capture the largest radiation amount so it is usually black painted or endowed with a selective surface (very absorbent to radiation and with low emissivity).

Paints are cheaper than selective surfaces and have a better overall thermal behavior at near-ambient temperatures, but are marred by ultraviolet radiation continued action and temperature variations between day and night.

Selective surfaces generally have a better behavior and are obtained by several layers superposition (metal and metal compounds) or special surface treatments.

The most modern manufacturing technique is laser welding.

3) Insulation: it is used to reduce thermal losses in absorber rear part that must be of low thermal conductivity. Materials can be glass wool, rock wool, cork, polyethylene or polyurethane.

4) Housing: generally made of aluminum or stainless steel, it protects and supports manifold elements, also allowing manifold anchoring and holding to assembly structure. It must withstand temperature changes (dilatations) without tightness losing and must resist corrosion.

Solar energy wherever you are with Sopelia.

Solar Layout is the App for collectors and solar modules on site positioning.

This is the most intuitive Solar App of the market.

To use it on field is not necessary to have an Internet connection because it works from place latitude, obtained by GPS.

Today we will see solar thermal energy part.

To begin press left command shown in initial screen with the house, the solar collector and the user taking a hot shower.

If our Smartphone GPS is not enabled, the App will ask us to activate it to locate our position.

Intermittent earth planet image immediately appear with the legend “Localizing”.

When our device GPS have located our position, the following screen appears to confirm it.

By confirming our location the Solar Equipment Use Menu displays.

There are 3 applications in the Menu:

1 Hot water: represented by a shower image
2- Heating represented by a radiator image
3- Outdoor pool conditioning: represented by a pool ladder image

By selecting one of the 3 applications, Options Menu will display.

There are 3 variables in the Menu:

1- Inclination: represented by collector and angle image
2- Orientation: represented by collector and cardinal points image
3- Distance: represented by 3 collectors rows image

By pressing the Inclination option, we get recommended inclination value for location and solar application selected, accompanied by some Tips considering collector type used.

Pressing Orientation option, we obtain procedure to fix collectors orientation description and access to recommended compass App discharge, if we don´t have it.

Pressing Separation option, the Kind of Surface Menu is displayed for us to select the appropriate option (Horizontal / Non horizontal). If the surface on which the collectors will be placed is horizontal, we only must enter Collector Height in cm data.

If the surface on which the collectors will be placed is non horizontal, in addition to Collector Height in cm data, we must enter Surface Inclination Angle data. We will enter a positive value if it matches the collector inclination direction and a negative value if it is different.

In this way we obtain the Separation (distance) between collector’s rows in meters.

Pressing i button Tips related to shadows and singular locations (snow, desert and rain areas) are deployed.

Download Solar Layout and placed solar thermal collectors on site in the most intuitive way with Sopelia.

Este cronograma representa la dosificación recomendada de dedicación para una correcta asimilación de conocimientos durante el curso e-learning de Técnico – Comercial en Energía Solar Térmica impartido por Sopelia.
Puedes recibir esta formación íntegramente desde tu computadora, smartphone o dispositivo móvil.
Supone dedicar entre 1 y 2 horas diarias entre lunes y viernes de cada semana.
* Semana 1: Introducción a la Energía Solar
1.1) El futuro de la energía solar
1.2) El Sol
1.3) Nociones básicas de Física
* Semana 2: Introducción a la Energía Solar
1.4) Nociones básicas de Electricidad
1.5) Nociones básicas de Energía
1.6) Energía del sol
1.7) Tablas
– Resolución Test 1 y 2 y Ejercicio 1
* Semana 3: Energía Solar Térmica – Equipos
2.1.1) Colectores
2.1.2) Sujeción y anclaje
* Semana 4: Energía Solar Térmica – Equipos
2.1.3) Fluido caloportador
2.1.4) Protección de la instalación
* Semana 5: Energía Solar Térmica – Equipos
2.1.5) Tuberías
2.1.6) Tanques acumuladores
2.1.7) Intercambiadores
* Semana 6: Energía Solar Térmica – Equipos
2.1.8) Grupos de bombeo
2.1.9) Aislamiento
2.1.10) Otros componentes
– Resolución Test 3 y Ejercicio 2
* Semana 7: Energía Solar Térmica – Instalaciones
2.2.1) Principios básicos
2.2.2) Diseño
2.2.3) Regulación
* Semana 8: Energía Solar Térmica – Instalaciones
2.2.4) Proyecto de un sistema de ACS
2.2.5) Cálculo de la superficie colectora
2.2.6) Cálculo de los demás elementos de la instalación
* Semana 9: Energía Solar Térmica – Instalaciones
2.2.7) Presentación de un proyecto
2.2.8) Otras aplicaciones
2.2.9) Ejecución y mantenimiento de la instalación
* Semana 10: Energía Solar Térmica – Instalaciones
– Resolución Test 4 y 5 y Trabajo Práctico final
Se trata de la formación en Energía Solar con la mejor relación calidad-precio del mercado.
Puede recibirse donde quiera que estés.
Solamente se necesita una computadora, smartphone o dispositivo móvil y conexión a Internet.
Por tratarse de la 1era edición hay un 50% de descuento sobre el PVP.

Esta acción de formación brinda capacitación técnico – comercial en aplicaciones domésticas de energía solar con el objetivo de difundir la tecnología y desarrollar recursos humanos para su incorporación al mundo laboral y empresarial.
La edición 2016 comienza el día 19 de septiembre y finaliza el día 25 de noviembre.

El plazo de inscripción es hasta el día 16 de septiembre inclusive en www.energiasrenovables.lat
Ya no tienes excusas, energía solar donde quiera que estés con Sopelia.

On Internet we can find free tools for basic or low complexity solar systems dimensioning and for certain components or accessories estimation.

Sopelia research team has carried out an exhaustive search and testing from which a new corporate website section called Free Solar Tools has been created.

Selected tools were classified into 4 categories.

Today we will analyze the third of them: Solar Thermal.

In first category we have already analyzed tools to obtain data about solar resource and other variables to be considered in energy estimation solar system will provide in our location.

In the second category we have analyzed tools to calculate the “load”, ie the energy demand to be met.

Now we are going to analyze tools to solar thermal system dimensioning and others to estimate individual components of a system.

The order of the tools is not random. We have prioritized the most intuitive, the most universal and those that can be used online without download.

For this third category our selection is as follows:

1) Solar Thermal Calculator

Approximate calculation tool from which budget, production data and system performance study is automatically obtained.

A Navigation Guide and Manuals can be found at page bottom.

2) Simulation for Solar Thermal System Pre-design

Online application based on the TSOL software that allows solar energy system simulating to ACS and ACS + heating contribute.

Available in German, English, Spanish and French.

3) Solar Fraction Calculation

Free download program developed by IDAE (Institute for Energy Diversification and Saving) and ASIT (Solar Thermal Industry Association) that allows to define a wide variety of solar systems introducing a minimum of project parameters, associated to each system configuration; and in this way, obtain solar system coverage on ACS and pool conditioning energy demand.

4) Solar Expansion Vessel Calculation

Tool developed to calculate solar expansion vessel volume.

Volume values (total circuit, solar collectors, pipes), Maximum system temperature (ºC), Glycol concentration (%), Height between expansion vessel and system highest point (minimum value 1 Bar) and safety valve Pressure setting must be introduced.

5) Thickness Insulation Pipes Calculation

Calculator that allows to estimate minimum and more economical water pipes insulation thickness.

Pipe Grade and Size, Insulation Material, Humidity and Temperature (Internal and Ambient) must be entered.

Solar energy wherever you are with Sopelia.

Thermal solar collector is responsible for capturing solar radiation and converting its energy into heat energy.

A body exposed to the sun receives an energy flow Er and heats up.

Simultaneously, thermal losses occur due to radiation, convection and conduction, which grow as the body temperature increases.

There comes a time when thermal losses Ep equals the gains due to the incident energy flow, reaching the so-called equilibrium temperature:

 Er = Ep

The equilibrium temperature of the collectors is usually between 100º and 150º C under normal conditions of use and for irradiation values in the order of 1,000 W / m2.

If it is possible to continuously extract a part of the heat produced Ee to take advantage of it as usable energy, the equilibrium conditions change:

Er = Ep + Ee

Ep is now smaller because a part of the energy received Er is tapped Ee.

The body has become a solar thermal collector.

If we want to increase Ee we have two options: reduce thermal losses Ep or increase energy flow Er.

First option involves collector design and construction improving in order to reduce losses.

For the second option is used the concentration technique, which by some optical system concentrates the solar flux on a smaller surface so that as the area decreases, the intensity increases.

In a solar collector the energy is extracted through a fluid called heat carrier.

The greater the difference between operating temperature and ambient temperature, the greater the thermal losses and thus the lower energy amount that heat transfer fluid will be able to extract.

The collectors must be operated at the lowest possible temperature, provided that temperature is sufficient for the specific use in each case.

This is because collector efficiency decreases as the operating temperature increases.

Improved insulation helps thermal losses reduce.

Reflection losses are due to transparent cover that usually exists in almost all collectors.

It will be necessary to properly orient the collectors so that they receive the greatest radiation amount possible during the period of use.

The question: which is the best collector ?

A priori has no answer.

It will depend on system location and energy demand that is intended to be met.

There are many types of solar collectors, but there are two large groups: unconcentrated collectors and concentrated collectors.

Solar thermal collectors according to their working temperature:

1) Low temperatura

1.1) Flate: protected and not protected

1.2) Vacuum tubes: direct flow, heat pipe and solar concentrator CPC)

2) High temperatura

2.1) Parabolic Cylinder

2.2) Central receiver system

2.3) Parabolic disks

2.4) Solar chimney

3) Other collectors

3.1) Rubber

3.2) Spherical

3.3) Conical

In next posts we will analyze in detail each collector type.

This content was extracted from the Solar Thermal Energy Technical-Commercial Manual and is part of Solar e-learning.

Solar energy wherever you are with Sopelia.

Solar thermal energy systems for domestic applications will be increasingly present in the built landscape and will be promoted by regulations such as solar ordinances or future building technology standards.

The most basic system is the compact equipment called thermosiphon, which incorporates all subsystems and where the fluid circulates naturally (difference in densities).

Solar thermal systems use the sun’s rays to get hot water or air.

Special plates, called collectors, concentrate and accumulate Sun heat and transmit it to the fluid we want to heat.

This fluid can be home’s drinking water or home’s heating or cooling hydraulic system.

Generally a thermal solar energy system is constituted by several subsystems, which in turn can be considered as interdependent systems connected to each other.

However, sometimes the same physically independent element performs several functions within the solar system.

These different subsystems are:

a) Capture system: composed of solar collectors. They are responsible for receiving the solar radiation and transmit it to the fluid that circulates inside.

b) Accumulation system: composed of one or more deposits to accumulate the hot water generated up to the moment of its use.

c) Hydraulic system: composed of the pumps and pipes through which the working fluid circulates. A primary circuit transports the energy captured to the accumulator. The circulation of the fluid through the pipes is performed by a circulation pump or by natural circulation.

d) Exchange system: exists in case the fluid flowing through the solar collectors is not the same as the one used by the user; for example when there is frost risk or user fluid can damage the solar system. The exchanger can be part of the same accumulator or located outside.

e) Control system: in pumps forced circulation systems will be in charge to start and stop them. Different components system actuation (motorized valves, pumps, etc.) is done through control mechanisms.

f) Auxiliary energy system: generally solar system economic viability requires that total energy demand cannot be met with solar input at all times. The energy produced by solar system depends on climatic conditions and that is why an auxiliary energy production system is available. These support equipment complement the solar system in order to ensure at all times hot water service continuity.

Solar thermal systems have a great similarity with conventional thermal systems.

In fact, they share all their components (pipes, protection mechanisms, accumulation tanks, exchangers, pumping groups, insulation) except one: solar collectors.

This content was extracted from Solar Thermal Energy Technical & Commercial Manual and is part of Solar e-learning.

Solar energy wherever you are with Sopelia.

Solar Layout is the App for collectors and solar modules on site positioning.

This is the most intuitive Solar App of the market.

To use it on field is not necessary to have an Internet connection because it works from place latitude, obtained by GPS.

Today we will check solar thermal energy part.

To begin press left command shown in initial screen with the house, the solar collector and the user taking a hot shower.

If our Smartphone GPS is not enabled, the App will ask us to activate it to locate our position.

Intermittent earth planet image immediately appear with the legend “Localizing”.

When our device GPS have located our position, the following screen appears to confirm it.

By confirming our location the Solar Equipment Use Menu displays.

There are 3 applications in the Menu:

1- Hot water: represented by a shower image
2- Heating: represented by a radiator image
3- Outdoor pool conditioning: represented by a pool ladder image.

By selecting one of the 3 applications, Options Menu will display.

There are 3 variables in the Menu:

1- Inclination: represented by collector and angle image
2- Orientation: represented by collector and cardinal points image
3- Distance: represented by 3 collectors rows image.

By pressing the Inclination option, we get recommended inclination value for location and solar application selected, accompanied by some Tips considering collector type used.

Pressing Orientation option, we obtain description of procedure to fix collectors orientation and access to recommended compass App discharge, if we don´t have it.

Pressing Separation option, the Kind of Surface Menu is displayed for us to select the appropriate option (Horizontal / Non horizontal).

If the surface on which the collectors will be placed is horizontal, we only must enter Collector Height in cm data.

If the surface on which the collectors will be placed is non horizontal, in addition to Collector Height in cm data, we must enter Surface Inclination Angle data.

We will enter a positive value if it matches the collector inclination direction and a negative value if it is different.

In this way we obtain the Separation (distance) between collector’s rows in meters.

Pressing i button Tips related to shadows and singular locations (snow, desert and rain areas) are deployed.

Download Solar Layout and placed solar thermal collectors on site in the most intuitive way with Sopelia.