Active solar surface: m²
The specific collector parameters are not usually related to the gross surface area but to the active solar surface, derived from the testing centre reports. Depending on the testing centre, the active solar surface of flat plate collectors is either the absorber area or the → aperture area. With evacuated tube collectors (e.g. with mirror constructions and vertically-standing absorbers), the active solar surface is often a purely theoretical value.
Annual heating requirement: Qh [kWh/a]
The total heat which must be supplied to the rooms of a building within one year to maintain a target temperature (building energy).
Annual heating requirement, specific: qh [kWh]
The heat, based on the floor space, that must be yielded within a year to maintain a target temperature in the building (effective energy).
Annuity: A
A series of equal payments, allowing for → lifetime and interest rate, for repayment of a capital debt. It is the product of annuity factor and investment sum.
Anti-Legionnaire’s switch: LEG
The guidelines of the German Association for Gas and Water specify that the entire content of the storage tanks and the piping in systems with a drinking water storage tank size of 400 liters and domestic hot water pipe content of over 3 liters must be heated to 60° once a day. The hot water storage tank is loaded in adjustable intervals in systems with an anti-Legionnaire’s switch.
Annual energy requirement: Final energy requirement
Aperture: Aa (m²)
Largest projected area through which unconcentrated solar irradiation enters the collector. In flat plate collectors, the area of the collector covering through which solar irradiation can penetrate the inside of the collector housing (light penetration area). In evacuated tube collectors, the aperture is the product of the length and width of the absorber strip and the number of tubes. If evacuated tube collectors are fitted with a reflector (→ CPC), the aperture is equal to the product of the length and width of the mirror surface.
Auxiliary heating: AuxH
Ensures that the → target temperature is reached even when there is insufficient irradiation. Where applicable, it also supplies the heating loop. Usually refers to the boiler.
A/V ratio:
The A/V ratio is the quotient of area to volume and is displayed in the unit 1/m.
Balance: (B)
→ Energy balance
Base load: [W, kW]
Minimum load / output an energy supply system must make available constantly during a period of use.
Boiler:
Serves to convert chemical energy into heat.
Boiler efficiency: η [-]
The boiler efficiency describes the relationship between the energy used by the boiler and the energy produced over a specific period of time.
Buffer tank: Buff
A storage tank filled with domestic hot water, usually in steel. The heat is transferred either internally via a serpentine pipe or outside the tank by means of an external heat transfer medium.
Building energy requirement: Qb [kWh/a]
Generic term for heating requirements, cooling requirements, energy requirements for hot drinking water, lighting, humidification.
Calculation of pollutants:
The solar system’s CO2 emissions savings are calculated. This is based on the emissions factors of the fossil fuel under consideration for heat generation. The emissions factors used here depend on the (saved) fuel. (→ fuel savings) → CO2 emissions
Capital value: V0
Sum of all → cash values of investments, subsidies, savings, operating costs, and loan costs (each signed). The interest rate used is equal to that which would apply when borrowing capital for the investment from a bank or at which the capital used could yield interest.
Cash value: [€]
Discounted future payments at the start of the period under consideration. A cash value is positive if it can be recorded as revenue and negative if the amounts represent costs. Items calculated are investments, subsidies, savings, and operating costs. → capital value
Circulation:
Circulation can be used for hot water preparation. This increases comfort (hot water is immediately available, even with long piping systems), but is also coupled with losses.
Clearness Index, Kt:
Kt = G/G0 , using global irradiation G and extraterrestrial irradiation G0
Climate: C
Climate is the current atmospheric conditions or a sequence of atmospheric conditions at a specific place which run their course over a specific period of time.
Climate data:
The climate data supplied with the program (for numerous locations) contains hourly median values for global radiation, outdoor temperature, and wind speed.
CO2 emissions: [g, kg]
(Carbon dioxide) is the quantitively most significant greenhouse gas (GHG) released by human activity (in particular combustion of fossil fuels). → Calculation of pollutants
Collector: Coll
Technical device for converting radiation energy into heat energy. Common types are flat plate and evacuated tube collectors.
Collector array: CA
The collector array consists of the collectors and the piping.
Collector loop: CL
Circuit containing the → collector or the → absorber and which is responsible for transporting heat from the collectors to the storage tank or heat transfer medium.
Collector loop connection:
The collector loop connection represents the connection between the → collector array and the storage tank by flow and return.
Collector loop efficiency:
Quotient of the energy emitted from the collector loop and the energy irradiated onto the collector area (active solar surface)
Collector power, installed:
= 0,7 kW/m² *A, with A: gross collector area in m²
Compound parabolic concentrator: CPC
Compound parabolic concentrator, reflectors used in evacuated-tube collectors for enlargement of the → aperture area in a geometrically optimized form as a parabolic trough.
Controller:
The controller has the responsibility of ensuring optimal operation of the system. Control parameters can be set for various components. For storage tanks, for example, target temperatures, switching temperatures.
Cooled: Cooled
Costs:
Consumption of goods to create and sell services and other goods.
Daily consumption: [l]
The average daily domestic hot water consumption. This is usually 35-45 liters per person and day at a water temperature of 50°.
Declared value for thermal conductivity: λ [W/(mK)]
Value of the → thermal conductivity of a construction material or product under specific external and internal conditions which can be considered typical of the behavior of this product when installed in a component.
Default data: Def.
Design temperature: °C
Temperature determined by the relevant climate zone as per DIN EN 12831 supplement 1 table 1a. The design temperature is the maximum (necessary) temperature of the heating water which suffices at the lowest winter temperature for the heating system to provide the building with required amounts of heat.
Deverter / injection system:
Special version of a control circuit. Particularly useful when the user is far away from the output but if required needs hot water promptly (often RLT)
DHW consumption: DHW con
DHW requirement: Daily consumption
DHW requirement, specific: qT
Diffuse radiation Gdiff [W/m²]:
Part of solar irradiation which strikes a horizontal or tilted surface via scattering through air molecules and mist particles or reflection on clouds.
DIN V 18599:
“Energy efficiency of buildings, calculation of net, final, and primary energy requirements for heating, cooling, ventilation, domestic hot water, and lighting”. Basis of calculations in German lawsEn.
Direct radiation Gdir [W/m²]:
Part of solar irradiation which strikes a horizontal or tilted surface without changing direction.
District heating DistHeat:
Heat supply for heating buildings and drinking water. In district heating, waste heat created during power generation (cogeneration) is used, among others. Transfer of heat is predominantly effected via underground piping.
DKE:
German Commission for Electrical, Electronic & Information Technologies of DIN and VDE.
Organization in Germany responsible for creating standards and safety regulations in the field of electrical engineering, electronics, and information technology.
Domestic hot water WW:
Domestic hot water typically refers to warm drinking water and in contrast to heating or buffer tank water can be consumed.
Effective surface AN:
Reference value for confirmation in accordance with the Energy Act for Buildings (GEG), derived from the gross volume of the building. All area-based values are based on AN.
As a general rule, the living space is generally smaller than the floor space.
Efficiency Eff:
The → collector loop efficiency and the → system efficiency are calculated.
Electric heating element el HE:
Electrical auxiliary heating in the storage tank
Electrical power Pel [W, kW]:
The electrical power states how much electrical energy is used in a specific unit of time.
Elevation angle: Sun height
Energy E (Joule):
Energy is the ability to perform work. The forms of energy are divided into mechanical energy (kinetic and potential energy), thermal, electrical and chemical energy, radiation energy, and nuclear energy.
Energy balance:
Comparison of incoming and outgoing energy flows in a system: the sum of energy supplied, energy released, and the storage of energy by the heat capacity of the system components must be equal to zero. Balancing is not carried out wholesale for the entire system but for the individual system components.
Energy input E, Qzu [Wh, kWh]:
Energy supplied to a component, e.g. irradiation, heat supply at the heat exchanger or heat transfer by mass flow due to consumption or circulation.
Energy output Qab [Wh, kWh]:
Energy (heat) transferred from one component (collector loop, storage tank, etc.) to another component or the environment.
Energy produced by solar system Qab [Wh, kWh]:
Comprises the energy transferred to the standby tank from the solar tank due to consumption and any existing return circulation control in the solar tank.
Energy supply:
→ Energy input
Expenditure factor:
System expenditure factor
External financing:
Part of the capital commitment is covered not by personal capital but by taking out loans. If the loan interest is higher than the capital interest, borrowing incurs further costs.
Final energy requirement QE [kWh/m²a]:
Calculated amount of energy available to the system technology (heating system, ventilation and air-conditioning system, hot water heating system, light system) to ensure the set inside temperature, heating of warm water, and desired lighting quality over the whole year. This amount of energy includes the auxiliary power required to operate the system technology.
The final energy is transferred at the “interface” of the building’s external envelope and thus represents the amount of energy required by the user for use as intended under normative boundary conditions. The final energy consumption is therefore stated by energy sources used.
Flow FL:
Flow generally denotes the warmer string in a heat loop. In a solar loop, flow corresponds to the pipe from the collector to the storage tank.
Fresh water requirement:
here: the domestic water supplied to the swimming pool for filling.
Fresh water station:
Hygienic domestic hot water heating with the help of a plate heat exchanger in a continuous flow process, compact station with heat exchanger, pump, controller.
Fuel consumption:
The calculation of fuel use (natural gas, oil, wood pellets, district heating) is derived from the energy transferred to the auxiliary heating heat exchanger via the fuel’s heat equivalent and the auxiliary heating efficiency.
Fuel price [€/kWh]:
The price for the stated final energy valid at the time of calculation. It must be entered in the currency given in Windows’ country settings.
Fuel saving [€/a]:
Fuels are primarily used to generate heat. In addition to reducing heat loss, the use of solar heat generates fuel savings. The program converts the available solar heat at any one time, using the respective auxiliary heating efficiency and the corresponding heat equivalent of the energy source, into fuel savings.
Global irradiance G (W/m2):
Hemispherical irradiation onto a horizontal surface.
Gross collector area AG (m2):
Surface area of the collector excluding devices for attachment and the piping connection. Usually width by length. Calculated by the external dimensions of the collector; the specific collector parameters are not usually taken from the gross area but from the → active solar surface.
Heat exchanger HE:
Heat exchangers are used when heat is to be transferred between different heat transfer media. Internal and external heat exchangers are differentiated.
Heat gains Qs, Qi:
Comprise the solar heat gains (dependent on the window area, type of window, and inclination) and the internal heat gains (e.g. produced by electrical appliances).
Heat load ΦHL [W, kW]:
→ Standard heat load
Heat loss rate [W/K]:
Product of heat transfer coefficient and the surface of the heat exchanger. The value is equal to the quotient from transferred power and median logarithmic temperature difference at the heat exchanger.
Heat losses:
Thermal losses occur through piping, radiation, and convection of heat in a collector. With selective absorber coatings, good thermal insulation or a vacuum, thermal losses can potentially be kept as low possible.
Heat requirement Qh [kWh]:
The heating capacity required to maintain a target room temperature in a building (net energy).
Heat requirement HR:
→ Standard building heat flow requirement
Heat transfer coefficient U [W/(m²K)]:
The heat transfer coefficient of a component describes the heat flow (heat lost) on a temperature difference of one Kelvin per square meter of the component. This is the crucial heat insulation property of outdoor components. The smaller the heat transfer coefficient, the better its insulation efficiency.
Heat transfer coefficient (heat loss coefficient) of the collector k1 [W/(m²K)] k2 [W/(m²K²)]:
States how much heat the collector releases to its environment per square meter of active solar surface and temperature difference in Kelvin between the collector median temperature and the environment. It is split into 2 parts, the simple and the quadratic part. The simple part (in W/m²/K) is multiplied by the simple temperature difference, the quadratic (in W/m²/K²) by its square. This results in the typically stated efficiency parabolic curves.
Heat transformer:
→ Heat exchanger
Heating cost:
Calculated from the quotients of → investment, → operating costs, and the heat generated (taking into consideration → lifetime and → capital interest).
Heating flow Q Punkt Φth [W]:
Represents a quantitative description of heat transfer processes. The heating flow is an amount of heat (heat output) transferred in a given time; direction of flow always from area of higher temperature to area of lower temperature.
Heating loop HL:
A self-contained system for distributing heat from the heat generator to the user, flow and return flow temperatures are dependent, among others, on the transfer system to rooms to be heated. Two heating loops with different design temperatures can be defined in T*SOL, a high temperature heating loop for radiators and a low temperature LT heating loop for underfloor heating.
Heating network HN:
Concentration of heating requirements in heating output units of varying size in the form of district or local heating networks.
Heating temperature limit THG:
Minimum / maximum outdoor temperatures at which the heating is switched on or off. The heating temperature limit is dependent on the insulation class of the building.
High temperature circuit:
A heating loop with high flow and return temperatures, e.g. for use in radiators and similar.
Incident angle modifiers Kq:
Describe the reflection losses when the sun is not perpendicular to the collector area.
Installation:
The installation of the collector array is determined by the → tilt angle and the → orientation angle (azimuth). From the tilt angle and orientation angle, the → radiation processor calculates the irradiation on the tilted surface for a specific location.
Investment:
Typically long-term, targeted capital commitment to generate future yields. Investment costs here correspond to the system costs, less any subsidies.
Irradiation model:
The values saved in the → climate data for global radiation are divided into diffuse and direct parts according to the Reindl model.
Irradiation processor: Calculates irradiation on the tilted area from the installation and orientation angle of the collector array, taking into consideration the diffuse and direct parts.
Life (of loan): Period of time agreed for repayment of a loan.
Lifetime: The period of time stated by the manufacturer in which the system should remain operable.
Load profile: [W, kW] [%] Hot water consumption dependent on time. The calculation is based on the definition of different daily, weekly, and annual profiles.
Loading loop: LL → Storage charging loop
Loading time: [h] Describes the period required for the storage tank to be loaded fully (supply of energy).
Loan capital: The amount of the loan taken out. It bears interest and must be repaid.
Loan interest: The amount of interest that has to be paid on a loan. If the loan interest rate is lower than the capital interest rate, borrowing a loan results in income from interest.
Local heating: LH Local heating describes the transfer of heat between buildings over relatively short distances in comparison with district heating.
Low temperature circuit: Heating loop with low flow and return temperature, e.g., for use with underfloor heating
MeteoSyn: Program for generating climate data.
Nominal size: [-] [mm] States the diameter of a pipe. DIN nominal piping sizes are used to calculate the collector loop piping widths.
Off: Switch in a program dialogue box.
On: Switch in a program dialogue box.
Operating costs: [€/a] Costs arising from the operation of the system, e.g., maintenance costs, electricity costs.
Operating period: (h) Each respective component is active during the operating period. A component is not active during specific time periods (hours, days, or months) that have been switched off.
Orientation angle: a (°) Describes the angle of deviation of the collector area from the south in the northern hemisphere.
Pay-back time: Period of time required until the total of returns on an investment reaches the amount of the investment.
Primary:
Primary loop: Heating loop in the heat generator with high temperatures for transferring heat with a heat transfer medium to the secondary loop.
Process heating: PH Process heating is the heating required for various technical processes and procedures (drying, cooking, melting, forging, etc.).
Proportional energy saving: as DIN CEN/TS 12977-2
Rate of price increase: [%] The prices for non-renewable energy sources are rising due to growing demand and increasingly scarce supplies.
Redirection valve: RV → Three-way valve
Return: R The return commonly describes the cooler string in a heating loop. In a solar loop, the return is the pipe from the storage tank to the collector.
Sankey graph: Graphic representation of energy or material flows using arrows, in which the width of the arrows is proportional to the width of the flow.
Savings: The simulation results include the reference fuel savings made during the simulation period through the use of the solar system.
Secondary loop:
Simulation: Test of the influence of ambient conditions, user behavior, and various components on the operating conditions of the solar system with computer calculations
Simulation period: Total period of time for which the simulation is to run. Simulation periods of between one day and one year are possible.
Simulation range: Time interval between 2 successive calculation steps.
Solar heat: Solar heat describes the conversion of solar energy into available heating energy.
Solar storage tank: The solar tank is the storage tank or part of a tank that is loaded from the collector array.
Solar yield: (kWh/m²) Energy released by the collector loop within a specific period of time.
Space heating: HL All technical elements and systems which serve to generate, store, distribute, and transfer heat.
Specific heat capacity: The amount of heat per m² of active solar surface that the collector, including its heat transfer medium content, can store at a temperature increase of 1 Kelvin.
SRCC: Solar Rating and Certification Corporation - USA
Standard heat load: HL [W, kW] Standard DIN EN 12831 (August 2003) describes the calculating procedure to determine the output of the heat generator and the heating surfaces required under normal design conditions to ensure that the required standard indoor temperature is reached in the rooms used in the building.
Standard heat requirement: QN,Geb (W; kW] Former term for heating load. The standard heat requirement is the basis for the dimensioning of the heat generator (boiler, solar system …). It states the required heating output to maintain the desired indoor temperatures (e.g. 20°C) in all rooms at the design outdoor temperature.
Standard outdoor temperature: Θe [°C] Outdoor air temperature used to calculate standard heat loss. It represents the lowest two-day median the air temperature has reached or dropped below 10 times in 20 years.
Standby storage tank: A system storage tank which is used exclusively for storing domestic hot water pre-heated to the target temperature (e.g. System A2).
Storage charging loop: Pump circuit for charging the storage tank → storage charging system
Storage charging system: Storage tank heating from bottom to top by means of a charging pump (storage charging loop), the heating surface can be located inside or outside the storage tank.
Storage model: Representation of loading and unloading processes The stratified storage model uses storage layers of variable strength. The number of layers in not fixed but adjusted during simulation.
Storage regrouping: Heat transport from the solar storage tank to the standby tank. When activated, storage regrouping occurs when a higher temperature is present in the solar storage tank (top) than in the standby tank (top).
Storage tank: ST To bridge weather-related and/or seasonal fluctuations in irradiation, storage tanks are used to buffer heat. The volume of the storage tanks is governed by the heating requirement and the period of time to be bridged.
Stratification: Facility enabling layered loading of storage tanks. Typical stratifications are e.g. convection chimneys with radial openings.
Sun height, angle of elevation: gs = sin h Angle of the sun to the horizontal. The solar altitude angle depends on the daytime, the time of the year and the geographical location.
Suneye: Device to determine an optimal location for the solar system with the help of annual irradiation graphs and sun-active time of day data.
Supplementary heating: → Auxiliary heating
Supply/removal: (To/Fro)
Surface A: see Effective surface AN
Swimming pool: SP
Swimming pool water heat requirement: The total amount of energy generated by the solar system and auxiliary heating for the swimming pool.
System efficiency: Quotient of the available energy generated by the solar system and the energy irradiated onto the collector surface (active solar surface). It is a benchmark for the system’s efficiency.
System expenditure factor: eP [-] The system expenditure factor describes the ratio of primary energy absorbed by the system technology in relation to the available heat released by it. The smaller the value, the more efficient the system. In residential buildings, the value for the energy requirements of a system also takes account of preparation of a standard amount of hot water. eP = QP / ( Qh + QTW )
Target temperature: The minimum temperature of domestic hot water If the target temperature in the upper layer of the tank is not reached, the → auxiliary heating is switched on.
Target value: Targ
Temperature: T (°C) The temperature is a material property and describes the ability of a body to generate internal energy in the form of heat.
Thermal buffer store: Contains heating water for heat storage.
Thermal conductivity: λ [W/(mK)] The thermal conductivity states the amount of heat passing through one square meter of a 1m-thick layer of building material in an hour when the temperature difference between the 2 surfaces is 1 Kelvin. Criterion for assessing the quality of insulating material.
Thermal engineering: Thermal engineering describes all aspects of energy conversion, storage, and transfer in machines and apparatus with the exception of electrical energy.
Thermal equivalent: Conversion process making energy sources comparable by their heat content (heating value).
Thermosyphon system: Operation in a closed circuit according to the gravity filtration principle without the use of pumps or controls.
Tilt angle: b (°) (inclination) Describes the angle between the horizontal and the collector surface. This is 0° when the collectors are flat on the ground and 90° when they are vertical.
VDE: Association for Electrical, Electronic & Information Technologies
Volumetric flow rate: Vp Flow [l/h] [l/m²h] The movement of a volume of a medium in a unit of time through the cross-section of a tube. The volumetric flow rate for the collector array is stated in l/h and can be specified either absolutely or relative to the collector area.
Zero-loss collector efficiency:
States the proportion of radiated energy absorbed by the collector on vertical incidence when the median temperature of the heat transfer medium in the collector is equal to the ambient air temperature.