APPLICATION NOTE 003

INSTALLING A DISO INTO A RENEWABLE ENERGY SYSTEM

By Benjamin Bacon, Owner, Plane Space Design

A Dual-Input Single-Output Unit (DISO) is a direct-current electrical power controller that is very useful in renewable energy systems in the same way that battery charge controllers are useful. The DISO is a protective device. Whereas battery charge controllers protect your batteries from being damaged by overcharging, a DISO protects your load from being damaged by loss of power. In other words, a DISO unit can be used to increase the reliability of a load being driven by a renewable energy system. In this way, whatever the service that the load is providing to its user, that service has better quality, is more reliable, and is made robust by the presence of a DISO in the power system.

In this application note you will be shown how to integrate the DISO into a renewable energy power system so that it functions optimally along with the other parts of the system. The three components of the most basic renewable energy system are one or more renewable energy sources that converts some natural phenomenon into energy, the battery bank that collects and stores the energy for later use, and the controller that moderates the process of delivery of the energy to its destination, be it directly to a load or to batteries. The DISO is now the fourth component, and it functions primarily for the benefit of the load, even though the energy storage components can benefit as well.

When the DISO is added it will connect on one end to two different sources of energy, a main source and a secondary source. The main source is the one with the primary responsibility of energizing the system, while the secondary source is reserved for occasions when the primary source fails to be capable of energizing the system. Another term that can be used for the secondary source is back-up. This description assumes that a DISO designed for current sharing is not being used, for with that type of DISO the distinction between Main and Secondary is relatively useless. The DISO for this application is assumed to be one for which the sources are treated as separate entities and either one or the other is actively energizing a system. The sources are isolated from each other to some degree, but to the system they appear to cooperate to keep it energized.

On the other end of the DISO is the single output. In the basic renewable energy system either the batteries or the controller can be connected to this interface. If the controller is connected to the DISO the batteries and other parts of the system that the controller protects continue to be protected. This, then is a good choice. On the other hand, if the batteries are connected to the DISO output, they will be subjected to reliable power without protection. Therefore it is recommended that the DISO be positioned between the energy sources and the controller in the system. In this way the system is reliable, robust, and protected. Downstream of the batteries, there may be further protection for the load but the DISO need not consider that component in most cases. Once energy is delivered to the controller, the DISO has served its function in the system. That is to keep a source of power available to the controller.

A DISO is a controller unit in the same way that a charge controller is a controller unit. The function of the DISO can be distinguished in a renewable energy system by designating it as a Source Controller. Renewable energy systems are greatly enhanced by adding a Source Controller, a DISO, to the set of components from which the system is composed.

In this application note the basic components of a renewable energy system were described. The functions of these basic components were described in turn. Then the DISO unit was described, and using its function as a guide the best position for installing the DISO in a renewable energy system was determined. As a Source Controller, the DISO functions to the best benefit of a renewable energy system when it is placed between the energy sources and the charge controller. Then it will supply reliable source energy to the controller and the system continues to be protected from receiving to much of the source energy. It is obvious that a renewable energy system that includes a DISO unit as one of its basic components is more reliable and more robust, and therefore, is much better than a system that does not.