Controlling a Solar Panel with a Buffer with two Heat Exchangers

Hint:

Use one solar control (Sol_SolarPanel) and one buffer macro (BUF_HeatBuffer).


At low solar power and due to the additional upper heat exchanger you can achieve higher temperatures in the buffer upper side as you could achieve with the lower heat exchanger only. The water volume you have to heat up is lower.

If the temperature difference solar panel temperature minus buffer middle temperature is higher than delta Ton, the solar panel changeover valve will switch to the “DHW” position and the solar fluid will flow through the upper and the lower heat exchanger of the buffer.

When the solar panel temperature gets lower than “BufferMidTemp” + delta Toff, but is still higher than “BufferLowerTemp + delta Ton, the solar panel changeover valve will switch to the “Buffer” position and the solar fluid will flow through the lower heat exchanger of the buffer.

Since the DHW priority is enabled, the changeover valve will always switch to DHW as soon as the (SolPanelTemp – BufMidTemp) > 5K (since we have connected the solar panel sensor to the DHW_TempSp.

When the solar panel temperature gets lower than “BufferLowerTemp” + delta Toff, the solar panel pump will stop.

You can find the plant schematic of this configuration in the next picture.

Fig. 6.   Controlling a solar panel and a buffer with two heat exchangers

Table 19.   Connections for a solar panel and a buffer with two heat exchangers

Inputs SOL_SolarControl

Connect to

SolPanelTemp

solar panel sensor

SolarPower

-999

FilteredOATemp

999

DHWUpperTemp

buffer upper sensor

DHWLowerTemp

buffer mid sensor

DHW_TempSp


solar panel sensor and enable DHW priority DHW-03 = 2

BufLowerTemp

buffer lower sensor

BufOverheatAlm


output BufOverheatAlm of the Buf_HeatBuffer

BufStopHighOAT

output BufStopHighOAT of the Buf_HeatBuffer