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BREEAM Lift Credits – Part II

BREEAM Lift Credits – Part II

This is the second article in a series on Lift BREEAM Credits. It explains and illustrates how to go about demonstrating compliance for several typical examples.

Other articles can be found by clicking the links below

BREEAM Lift Credits – Part I

BREEAM Lift Credits – Part III

The second part for your first lift BREEAM credit can be obtained by estimating the energy consumption for at least two types of lift or lift strategy ‘fit for purpose’ and the system with the lowest energy consumption specified.

So, there are two choices;

Estimating the lift energy consumption of at least two types of

1. Lift

2. Lift strategy

Both of the two type must be ‘fit for purpose’, which excludes unrealistic comparisons that could certainly not be argued as practical and ‘fit for purpose’.

We will deal with the easiest solutions first.

Scenario 1 – Single lift in low to medium rise building. A medium rise building for the purpose of this example is one with no more than 6 or 7 floors or a maximum of about 20m travel.

The two ‘fit for purpose’ lift types are hydraulic and electric traction. Both will almost certainly satisfy the lift traffic demand in the building as confirmed in the lift traffic analysis required for the first part of your first lift BREEAM credit.

There is one simple, significant difference between a hydraulically driven and an electrically driven lift. A hydraulic lift, lifts the weight of the empty car every time it moves up. Even if there are no people in the lift it must move the empty car. Although it does have an advantage when moving down as it uses mostly potential (gravity) energy which is free.

A traction lift is counterbalanced usually at about 50%. This means the weight of the counterweight is equal to the weight of the empty lift car plus half the rated load. So when the car is empty it is only driving the half the rated load. If the car is half full it weighs the same as the counterweight and the energy consumption is then very low to move the lift.

This counterbalancing of an electric lift against the fact a hydraulic lift moves the lifts weight in every up journey, when averaged over the daily cycle shows that the electrically driven lift is a far more energy efficient lift than an hydraulic one.

An easy way to satisfy this BREEM lift requirement is to use these arguments to demonstrate that you have compared an electric traction lift with an hydraulic one and you have specified the electric traction lift.

Scenario 2 – Comparing Lift Strategy

In any other scenario where the traffic demands on the lifts in the building require a group or groups of lifts (a group is considered as two or more lifts), you will be considering only electric traction lifts. This is because hydraulics lifts are limited by the number of lift starts per hour they can practically achieve, whereas electric lifts can achieve typically double the number of starts or more.

How to compare ‘fit for purpose’ strategies for groups of electric traction lifts?

Drive technology for modern electric lifts have reached a point where there is only one very energy efficient drive to choose and that is a variable-voltage-variable-frequency lift motor drive. The lift market is dominated by this type of drive so unless you have very unusual circumstances this will be the choice.

Geared versus Geared

Up to lift speeds of about 2.0 m/s you have a choice between using a geared lift (a lift driven by a motor through a gearbox) and a gearless lift (the motor directly drives the traction sheave).

All other things considered equal a lift with gearless drive will be more energy efficient than one with a geared drive because it does not have the energy loss moving the gears in the winding gearbox.

Parking Strategies

As part of identifying the best way for your lifts systems to cope with the demands on them, you can compare different locations for the lifts to park throughout the day to best suit demand. Different parking scenarios may be ‘fit for purpose’ but one may stand out that minimises the number of lift journeys or lifts stops and doing that will reduce energy.

Lift Kinematics

By this we mean velocity, acceleration, deceleration and Jerk. Identifying different set-up options in terms of these kinematic variables should certainly satisfy the ‘fit for purpose’ but can also have a significant impact on the energy use of the lift.

Control Systems

These can be very sophisticated and with larger groups of lift, more advanced control systems can ‘learn’ the traffic patterns in a building and optimally set up the group of lifts to respond in that demand in the most efficient ways. And they can do this dynamically so if the demand changes, the response changes.

These systems allow optimisation to meet the demand on different ‘traffic’ and ‘passenger’ variables for example by limiting journey time or by allowing only so many people in the lift or may minimise the number of stops. The method of optimisation will have an effect on the energy use of the lifts so some will be more efficient than others, whilst all can be considered ‘fit for purpose’

Applying one or several of the above factors will mean you have considered more than one lift strategy and that is enough to satisfy the second requirement for getting your first Lift BREEAM credit.

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