1. Uninterruptible Power Supply
Dave Swindells, Tom Robinson

2. Functions of a UPS
To ensure that the power supply is maintained during an interruption or fluctuations to the mains supply.
To provide a stable power supply, devoid from spikes and surges. This is essential for computer systems and similar systems.

3. Types of UPS Below is a list of the types of UPS: Static Rotational
Hybrid

4. Static
This type of UPS has no moving parts and generally comprises of a bank of batteries, a charger and an inverter. If there is a mains failure then the batteries supply power via the inverter which changes the DC supply into a usable AC supply.
Advantages: Few moving parts, easy to maintain, very quick changeover, quiet operation
Disadvantages: Batteries will run down over time
Application: Backup for servers and computer equipment that needs to be shutdown safely.

5. Online and Offline
Offline systems are the cheapest available, during normal operation the mains supply passes directly through the system so are exposed to any minor changes in voltage. A limited amount of spike protection is provided but the overall protection is poor.
In contrast to the offline systems, online systems the battery, charger and inverter are operating at all times. The incoming mains AC supply is converted to DC power and then converted back to AC when required. This provides voltage regulation and spike protection to prevent damage to equipment.

6. Rotational
This type of UPS incorporates a motor/generator which provides clean and stable power for critical loads. These are usually powered by diesel. They contain an induction coupler which is an electro-mechanical flywheel which stores kinetic energy to get the generator running whilst the diesel engines are bought online.
Advantages: It can come online instantly because of the flywheel. It can run for a very long time depending on the size of the tank.
Disadvantages: Take up lots of room and are very noisy. Moving parts so maintenance is required.
Application: Backup for critical and non critical loads.

7. Hybrid UPS
This type of UPS uses batteries and an inverter to provide AC power alongside a generator, in addition other sources of power such as PV panels or wind turbines can be used to provide additional backup power.
Advantages: It has batteries and as such can come online instantly. It has other backup systems so electricity should be available at all times.
Disadvantages: More systems are required and as such it will be more costly to install.
Application: Backup for critical and non critical loads.

8. Conclusion
In conclusion for this building we believe that the Hybrid UPS would be the best option.
This is due to it featuring both rotational and static systems in one and also having power supplies coming from other sources of power.