1.9.4.1.Design steps of the simple solar system.

Let us consider a solar system for domestic hot water with gas boiler. The “domestic hot water” as consumers/load was taken and “solar system” as provider. The “All types” of “System Specification” parameters were selected and the template 8a:Hot Water (solar thermal, high-flow) was chosen for implementation.

Fig. 1.9.7 Schematic diagram of domestic hot water system – Template 8a.

The system consists of solar collector, boiler, tank, pump, three way valve, the source of water, hot water tap and pipes.

In the next three steps the parameters of main components – hot water demand, solar collector, tank and additional heat generator will be introduced.

Fig. 1.9.9 Three steps of design specific for solar collector system

On the beginning hot water demand must be defined. There are three possibilities:

• daily demand – directly input or calculated from the number of persons in the family (Polysun advices 50l/person/day)

• fixed annual demand

• profiled annual demand (there are six predefined profiles files: student’s house, early care home, hospital, residential building, summer camping site, all-year camping site and single family dwelling. Note: Educational version of Polysun has no possibility to create user’s profile files).

Designer can take into account absences of householders. The profile of the absences is set by opening function ‘Absences’.

Dimensioning of the solar thermal system:

• Test standard: test standard describes the parameters of collector and theoretical model taking to the calculation of the system. The possible standards are: ‘North America’, ‘Europe’, ‘China’

• Collector and Tank model is chosen from the catalogue

• Orientation

• Tilt angle

• Solar fraction (low, medium, high): user can choose between economical, low price and fast amortization system and ecological, high fuel savings system. Medium option is recommended.

• Recommended collector number: Polysun recommends a number of collector

• Gross area: computed total, active area of collectors

• Recommended tank volume: Polysun recommends a volume of a tank

• Tank – use choose a tank of recommended volume or similar from the catalogue

Heat generator - Polysun recommends a power of the boiler and user choose a boiler model from the catalogue.

1.9.4.2.Design steps of the pv system.

In Polysun the grid-connected systems can be designed. PV modules are wired in series and in parallel. Modules wired in series are called a ‘string’. Strings are wired to the inverter which converts DC current to the AC of public power-supply current. A set of inverter and modules is called a ‘field’. Each of the field has its own configuration of modules and all modules have the same orientation. Up to three fields can be defined in one variant of the project.

Fig.1.9.8 The steps of design specific for PV systems.

1.9.5.Result analysis and reports

After simulation of the designed system a user can view results and can prepare report for customer. A special model of abbreviations for energy balance description is used in POLYSUN. An abbreviation has up to 5 letters. The first letters are:

E	End energy (fuel and electrical consumption)
Q	Energy to the system or energy withdrawn from the system
S	Energy to the tank or energy withdrawn from the tank

Next three letters are:

sol	Solar energy
out	Energy withdrawn
use	Energy consumption
dem	Energy demand
aux	Auxiliary energy (energy of heat generators or air-conditioning devices)
dem	Energy demand (the amount of energy, theoretically calculated, required for example for heating cold water to desired temperature
par	Auxiliary or parasitic energy (pumps or fans)
int	Energy to indoor room, energy dissipated by all components placed inside the room
out	Energy to surroundings, energy dissipated by all components placed outside the room
def	Energy deficit (difference between demand and consumed energy)
xfr	Transferred energy
ventil	Energy in ventilation of building
trans	Energy transmission in building

Last letter:

S	Solar
A	Auxiliary
X	Heat transmission
U	User
M	Mixed (solar and auxiliary)
	Total of all loops

For example, in case of collector, E_sol is a gross collector surface irradiance but Q_sol means energy transferred by the collector to the fluid. E_aux is the energy carry in by other source of heat ie. gas heater.

Three kinds of effectiveness (solar fraction) are calculated for comparison of the systems – internal, net and gross.

Internal solar fraction SF_i is defined as:

where: S_sol – solar energy supplied to the tank

S_aux- heat generator energy supplied to the tank

Net solar fraction SF_n is defined as:

where: Q_sol – energy of solar collector to system

Q_aux- energy of heat generator supplied to system

Gross solar fraction SF_g is defined as:

where: E_sol – irradiance onto collector area

E_aux- total energy consumed by heat generator