18-0326 v3.1/Emergency Power System Approval Request 3.x

We ask for advice concerning the Imperative 06 Net Positive Energy for a NetZero project, particularly the exception I06-E6 4/2010 Emergency Power Systems.

We have been working together with the design and engineering team to find an alternative for diesel emergency power system for our 10,564 sq m project which is mostly composed of retail and service spaces.

Legal Requirements: In México, Official Law “NOM-001-SEDE-2012”, article 700, demands as a mandatory requirement the installation of an emergency power plant for this type and size of building; the same as required by NEC (National Electrical Code – NFPA). The latter in order to provide power in an emergency case, of electrical outage.

The engineering team has optimized the design of the systems in order to reduce the required energy of the emergency power plant, using high efficiency technologies and low energy consumption systems, such as regenerative elevators, batteries support for emergency signaling, and surveillance devices as possible.

Therefore the emergency plant has been sized to provide power only to: Emergency lighting, access control, surveillance systems, fire fighting system including fire detection, fire alarms, and ventilation and extraction in common areas, for up to 7 hours of operation.

Diesel combustion, which per NZEB is not an option, was not analyzed in detail, and our Engineering team mentions its operation range is very short.

Knowing that only propane gas  based generators may be used, our Engineering team analyzed the following options:

LPG Emergency Power System: Propane Gas is only available in Mexico as Liquid Petroleum Gas (LPG) which is a mixture of 60% Propane and 40% Butane Gas; is heavier than air and is highly flammable. This is an allowed technology to be used, but we consider this as a high risk option for the project and the users, because this emergency plant will require an on-site storage cylinder container located in a well ventilated ground level space. Considering the project’s location, in the middle of the financial and commercial center of the city and surrounded by residential buildings, it will be dangerous to have a LPG container which: 1) is highly explosive; 2) requires trained maintenance; 3) will generate noxious noise and emissions to surrounded projects during emergency operation; and 4) as the containers volume is sized according to the operations range, the cylinder will eventually need to be refilled, presenting another risk operation.

Natural Gas Emergency Power System:  Largely composed of methane. Natural Gas is delivered on site through pipeline, therefore gas storage is not required, and has a good safety record as is lighter than air, dispersing relatively easily in case of any leak. This system is also more energy efficient and will provide a better response in case of emergency. The Natural gas power plant also provides continuous operation as long as the service can be supplied to the pipelines. Gas Natural México, the company that supplies natural gas through pipeline, remotely controls the general emergency system to stop gas supply to the building and surrounding areas in case of risk, and refill maneuvers are not required. We strongly recommend this alternative to be used in the Project.

We are asking for advice to correctly grasp this specific requirement, and permission to use the Natural Gas Emergency Power System, which in our opinion represents a safer option, and results in better environmental and health benefits.

ANSWER:

Exception I06-E6 Emergency Power Systems has been amended to more clearly define situations when liquefied petroleum gas (LPG) is an acceptable alternative fuel.  

(4/2010) I06-E6 Emergency Power Systems

If programmatic needs, basic project function, or code requirements mandate the inclusion of an emergency power system beyond that required by the Imperative, an emergency power system is allowed. Battery backup power is encouraged. When battery backup power is not feasible, propane or equivalent (e.g. LPG systems) backup generators may be used if the generator:

is not included in the project’s strategy for operation and any use during the 12-month performance period is offset through the project’s renewable energy generation.

does not impact adjacent properties through noxious emissions or noise.

If storage tanks for emergency power pose a negative impact due to significant danger related to density or other factors (e.g. projects located in transects L5 or L6), the project team may include a hard-piped natural gas service to the emergency power system, if the gas service:

is not connected to the project’s primary energy systems

is sized exclusively for the emergency power system, and

includes a dedicated utility meter to account for any emergency use during the performance period. 

Propane-based emergency backup boilers are acceptable in harsh climates for non-grid-tied projects.

Diesel backup generators are not allowed unless the project meets another exception.

The project team will need to provide a narrative explaining the need for backup power, particularly with regard to the project’s size and function, and illustrating how every effort has been made to reduce the size of the system and prevent its use.

Documentation:

All projects using emergency power generation: 

I06-a Exception Narrative

Projects with a hard piped LPG system must also include: 

I06-b Metering Data 

I06-c Technical Documents  (addressing pipe sizing)