Integrating the solar generated steam directly into the existing steam line is a more promising option. In order to fit the solar boiler into the system identical technical standards as for the production steam line should be applied. This means that, for example, the piping materials used in the solar field have to be the same as in the production line, the chemical properties of the condensate should be the same, etc. In any case, due to safety regulations, the solar field and all the steam devices (valves, flexible hoses, steam drum, etc.) should have the “CE” mark and all welding must be done by classified welder for pressure equipment to pass the performance and acceptance test of the technical inspection agency.

If these basic requirements are fulfilled, the solar steam could directly feed into the production line by means of an overpressure valve (>4 bara), with the feed water to the solar steam generator provided from the industrial steam system. Condensate from the solar system can be tracked back by the condensate line of the existing system. The feed water pump for the solar field will be controlled by a level measurement in the steam drum. Figure 3 shows the system layout for this configuration. The steam drum is operated at constant pressure of about 4.3 bara.

During strong transients, that might have negative impact on the stability of the steam line, the generated steam can be blown off through a waste steam line above the roof. In this case, the production line is not affected. If the solar field is out of operation for an extended period, all condensate will be removed into a waste reservoir and the plant refilled with fresh feed water to avoid condensate degradation by corrosion and aging.

This option allows a very simple and compact balance of plant for the solar steam generator, and avoids cost and losses associated with additional piping and controls for the distribution. The solar steam generator is simply treated like any conventional supplementary boiler which might be retrofitted to an existing system.