Canadian Consulting Engineer

What’s New… (August 01, 2005)


August 1, 2005   Canadian Consulting Engineer


Toronto Zoo installs bi-fuel generators for emergency power

One of the largest zoos in the world, the Toronto Zoo houses over 5,000 animals and has plant collections representing six zoogeographic regions. Protecting these collections, many from tropical and sub-tropical locations, and maintaining the aquaria, the commissary, the animal hospital and public services such as washrooms is critical during power outages.

With emergency backup power only provided to six buildings in the zoo complex, the animal and plant collections would have been at risk during an extended utility failure. As well, six generators (five natural gas and one diesel) were nearing the end of their life cycle at 30 years of age.

The potential problem prompted Eric Morris, manager of facilities and services at the zoo, to initiate a feasibility study of a new emergency backup power system with an uninterruptible source of fuel.The system had to operate with minimal environmental impact. The Toronto Zoo has a mandate to promote operational practices that have a high standard of environmental protection.

The feasibility study by Morrison Hershfield showed 1,500 kilowatts were required to provide maximum emergency electrical power to all the zoo facilities, which include 46,500 square metres of pavilion, visitor and administrative space.This supply would allow the zoo to operate independently of the power grid. (The zoo is discussing paralleling opportunities with the local utility.) The recommendation was for four 375 kW capacity parallel generators in two gensets, which would accommodate 125 per cent of the peak winter power load.

The fuel source was critical.Liquid propane and hydrogen were ruled out as too costly in this application. Diesel powered generators are proven technology and cost efficient. However, diesel tanks generally hold only enough fuel for several days of operation. Natural gas generators are also proven technology, fuel is readily available and it is more environmentally friendly with respect to emissions than diesel.

A dual source of fuel offered the best solution. Bi-fuel generator technology, a combination of diesel and natural gas fuel sources, is not new (Rudolf Diesel began experiments with enriched combustion air mixtures in the early 1900s.), but has only recently become economically feasible in smaller generator units. Investigations of Gemini twin gensets from Generac Power Systems of Waukesha, Wisconsin showed that bi-fuel technology would meet the parameters of the project specifications. Running with up to 90 per cent natural gas and 10 per cent diesel fuel, the generator capacity run length is extended by eight times, from two days to 16 days. The bifuel system therefore provides the zoo with an extended buffer of protection, allowing sufficient time to refill the diesel tank should the power be out for a long period. If the natural gas supply is interrupted, the generators automatically revert to full diesel operation.

The natural gas/diesel combination significantly lowers exhaust emissions. In comparing a 375 kW, 12.0 L generator with bi-fuel capacity to a straight diesel mode engine, it was found that the measured NOx emission (grams/brake horsepower-hour) were reduced by over 20%, and particulate matter by more than 60%.Operating at a 90/10 per cent fuel ratio, NOx emissions are in the range of 6 to 12 parts per million, only slightly higher than straight natural gas.

The incorporation of a natural gas valve and regulator into the standard diesel engine is a minor cost factor considering the flexibility the system provides compared to a generator running on a single fuel source. When it is initially started up, the standard turbocharged diesel engine operates on 100 per cent diesel fuel. As the engine reaches its operating temperature, a metering system feeds natural gas into the incoming air supply. Because natural gas ignites at a higher temperature (620o to 650o C) than diesel (260o to 400o C), the heat generated during compression is not sufficient to ignite the gas. In the bi-fuel system, a small amount of diesel fuel is sprayed into the cylinder. Ignition of the diesel fuel ignites the air/natural gas mixture. As more loads are applied, an increasing amount of natural gas is mixed with the intake air as a microprocessor cuts back on the amount of diesel injected, adjusting to the optimal bi-fuel mixture. The process allows the engine to operate without any reduction of performance, giving the full power of 100 per cent diesel operation while running on up to 90 per cent natural gas. Sensors adjust the fuel mixture to prevent knocking before it occurs.

The four generators, supplied by Total Power of Mississauga, Ontario, are controlled by one transfer switch, which automatically switches to the generator power when the utility supply is lost. Generac’s modular power configuration of two sets of two generators with built-in paralleling capabilities synchronizes the units and eliminates the need for paralleling switchgear which is very costly in systems under six megawatts. The modular configuration is also more economical than a single large unit, while providing greater reliability and flexibility.

The load requirement is automatically shared across the twin gensets. This redundancy provides an internal backup system. Should one generator shutdown, or be taken out of service for maintenance, the remaining units take up the load shed. The configuration also allows additional gensets to be incorporated as required.

Although the backup generator system supply is at 600 volts, this is stepped up to 27,600 volts (utility voltage) for the facility’s total electrical load to be transferred through an open transition high voltage transfer switch. The change is done within 45 seconds of a utility power interruption.

By Ahmad Alsaad, P. Eng., senior electrical engineer with Morrison Hershfield of Toronto, written in collaboration with Total Power of Mississauga, Ontario.


Internet Protocol (IP) video surveillance

Every project needs to be designed with physical security in mind, be it a building, power plant, highway or water filtration plant. Poor security design can threaten people’s safety as well as expose assets to theft and vandalism.

Although video surveillance equipment has been around for a half- century, the past decade has seen a technological revolution in the capabilities of these systems.

The majority of video surveillance systems in place today are based on analog technology developed back in the 1950s and improved over the decades. The architecture is comprised of analog cameras connected through coax cabling to a matrix switch. The matrix switch redirects the video feeds to analog monitors as well as to videocassette recorders (VCRs). A CCTV keyboard controls the system.

A large physical footprint is required for these systems. Electrical wiring is necessary to power each system component. Coaxial cable needs to be pulled through walls and ducts to a central location in a building where the video images are viewed and recorded. Furthermore, the security control room must be fairly large to accommodate the extensive equipment and wiring.

With the revolution in computer technology in the 1980s and 1990s, digital video recorders (DVR) replaced VCRs. DVRs store video on hard drives, which improved storage and searching capabilities. The digitization of video also opened the door to an entirely new set of functions, including digital motion detection, digital zooming and the export of video into standard video files that could be transferred onto a CD.

However, the architecture of a DVR system varies only slightly from the traditional analog approach to video surveillance and has the same physical drawbacks. It requires extensive coaxial cabling and a large centrally located room. And the core of these systems is either a DVR or matrix switch. The failure of one
of these components means that data from the entire block of cameras managed by that DVR or switch is lost.

Traditionally set-up systems also lack scalability. They are expanded with the addition of either another matrix switch or DVR. Usually this type of hardware comes with camera inputs of 8, 16 or 32. When expansion must be done in such large blocks, security managers are sometimes hesitant to assume such a large expenditure.

Each DVR is self-managed. As a result it is difficult for the security staff to understand what is occurring throughout a multiple DVR system. Additionally, these systems offer little in the way of third party integration with other systems such as access control, HVAC and building automation. They have to be controlled through separate interfaces. A system with this degree of decentralization hinders security managers’ ability to respond quickly and effectively to events.

IP systems

A solution to the above problems is an IP (internet protocol) system. An IP system is networked-based and works over wide area networks (WAN), local area networks (LAN) and the internet. IP systems use CAT-5 cabling which is already in place in most establishments.

IP systems are built on an entirely different architecture than analog and DVR systems. They transmit video, audio and data across an IP network in a distributed architecture. Cameras, servers and workstations can be added to the network at any time, expanding by one camera at a time, up to thousands of cameras. Open architecture also allows for easy integration with other systems such as building automation, and the data can be viewed anywhere, on any device with an internet connection.

IP systems are extremely reliable. Their distributed architecture eliminates any single point of failure and technologies such as redundant and fail-over archiving ensure that users have access to all data at all times.

Article supplied by Genetec Information Systems, Montreal, written by Brett Beranek. The company develops and markets Omnicast, an IP based video surveillance system.

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