Not ESD Savvy – 5 Stars is still within reach

Simple Ways to Save Energy

This post discusses simple ways to save energy. It is expected this post will be updated regularly.

Also see ‘Natural AHU’ Post

You don’t need to be ESD Savvy

So how do we consume energy?

  • Lighting to see
  • Electrons for power
  • Cooling and Heating to feel comfortable and air to breath
  • Hot Water
  • Etc

 

 Commercial Sector Buildings Energy End Use (2006)
Commercial Sector Buildings Energy End Use (2006)

Source: DOE, 2008 Buildings Energy Data Book, Section 3.1.4, 2008.
Note: This pie chart uses an adjustment factor (*) used by the EIA to reconcile two datasets.

STEP 1: Stop Energy Loads, At Source, including:

  • Lighting
  • Cooling
  • Heating
  • Hot Water

STEP 2: Make Systems as Efficient As Possible:

  • Lighting
  • Cooling
  • Heating
  • Hot Water

STEP 1: Stop Energy At Source

Lighting to See

  • Use Natural Light
  • Get rid of the concept of providing high levels of lighting everywhere. Provide desk lighting with individual user on/off control (with LED bulbs).
  • Use LED Lights (no excuses, technology and pricing is here)
  • Turn those lights off. LED lighting can come with individual sensors. If a room is unoccupied, the lights go off.
  • Zone your lighting to take account of natural day light
  • Use light colours

Cooling

Step 1: Stop the heat coming in. As a minimum comply with the BCA.

  • Think about operable blinds
  • Use great glazing
  • Insulation
  • And Insulation. Get real and check the Actual U values (Thermal Bridging).
  • Seal the Building. And get it checked…air pressure test.

Infiltration especially in older building is a big issue.

LOAD EXAMPLE:

An office of say 1500 m2 and 2.8 m high

Poor façade: infiltration at 0.5 ac/hour: Cooling load: 8 kW each hour (of additional cooling).

Better façade: infiltration at 0.2 ac/hour: 3.4 kW each hour (of additional cooling).

  • Use low energy consuming equipment

Step 2: reduce your outside air supply  & temperature.

  • Monitor the air quality and reduce outside air (CO2 monitoring).

I’m modern offices, home working and hot desking is the norm. Thus on any given day the number of occupants (driving outside air requirements) is less than design (typically 1 person per 10 square meters). BUT the plant continues to deliver design outside air.

At certain times of the year the office occupancy is down to a skeleton crew…BUT the plant continues to deliver design outside air.

  • Have smaller zones. If no occupants turn off the outside air
  • Pre cool the outside air with:
    •               Room air, already cooled
    •               Thermal labyrinths
    •               A water feature
    •               Air intake from shaded location

Step 3: Increase the room air temperature. What’s wrong with 27 oC instead of 24 oC?

Step 4: Just like lighting, who says a whole floor needs to be at a constant uniform temperature.

Also, using those LED occupancy sensors that come with those LED lights, turn off AC to areas that are not occupied.

  • Consider communal open plan areas at 27o
  • Consider a small fan for each user on their desk.
  • Consider a high velocity VAV cold air duct system to provide localised spot cooling.

Heating   

Step 1: Stop the heat getting out. As a minimum comply with the BCA.

  • Think about operable blinds (let sunlight (heat in)
  • Consider the glazing type
  • Insulation
  • And Insulation. Get real and check the Actual U values (Thermal Bridging).
  • Seal the Building. And get it checked…air pressure test.
  • Pre heat hot water from waste or solar sources.

Step 2: reduce your outside air supply temperature.

  • Monitor the air quality and reduce outside air.
  • Have smaller zones. If no occupants turn off the outside air
  • Pre heat the outside air with:

Room air already heated

Thermal labyrinths (SOL Air)

Air intake from a sunny location

Step 3: Decrease the room air temperature. What’s wrong with 19 oC instead of 24 oC?

Step 4: Just like lighting, who says a whole floor needs to be at a constant uniform temperature.

  • Consider communal open plan areas at 19o
  • Consider a high velocity VAV warm air duct system to provide localised spot cooling.

Step 5: Temperature Drift (End of Day)

At the end of the day, let the room temperature drift upwards, allowing a larger buffer, so in the morning the space needs less energy input to get back up to temperature.

Hot Water (Not Drinking Hot Water)

  • Limit the amount of hot water you need
  • Lower water temperatures (avoid heating up to only blend down)
  • Pre heat mains cold water with the sun
  • Heat hot water with the sun
  • Limit pipe lengths to avoid long warm up delays
  • Turn off those zip heaters

 

All the above are simple ideas and any engineer can incorporate into a design. Get these right and you’re on the way to a 5 star building.

STEP 2: Efficiency Improvers

Add some more of the following efficiency measures, and things only get better:

  • Don’t use electricity for chillers.

Got roof space? If yes consider evacuated solar tubes (Other collectors available). These systems will heat water to the required temperature (c. 95 oC) to use in absorption chillers.

Thermax Hot Water Absorption Chillers

hot-water-driven-chillers-img[1]

Solar Cooling (Simplified Schematic)

solar-based-cooling[1]

  • Efficient  Chillers  (HIGH COP’s)

If you have to use electric chillers then use the best available (Highest COP). Don’t forget this is where you should spend your money…this is the biggest energy consumer in your building…the backbone of your HVAC system.

Chiller Efficency

Consider chillers that use:

  • Permanent magnet motor
  • Active magnetic bearings
  • Oil free system

 

  • Efficient Chiller System Design (Pipework)

Consider non traditional pipework system to increase chiller efficiency, such as Series Counter-flow.

Series Counter Flow Chillers

Series Counter Flow ChillersTraditionally large central plant chillers have been connected in a ‘parallel’ pipework system. Each chiller receives the same condenser water temperature &chilled water return water temperature and cools and delivers chilled water at the desired temperature. Each chiller does the same ‘work’.

the two chillers in the diagram above, are acting as a two-stage chiller, sharing the waterside lift and resulting in lower lift for each chiller compared to parallel piping and is thus more efficient. Thus overall the system efficiency is increased.

Note: Series counter flow adoption is not always the best option. Factors such  as climatic conditions, building cooling load
profile, the use of economy cycles, airside system design and utilisation schedule all play a part in determining the viability of this pipework arrangement.

  • Adiabatic cooling. This is using wet bulb free cooling (water sprays)
  • Economy cycles. Using cooler air than inside air t do the cooling for you.
  • Night Purge/Building Flushing
  •  Smaller Thermal Zones

The smaller the thermal zone the less over supply of air will occur to a floor. PCA Premium grade buildings typically use 80m2 zone sizes for perimeter areas and 120 m2 for interior zones, with each zone having 1 VAV box controlling air to that zone.

Imagine each diffuser sensing the temperature of the air local to itself and modulating the air supplied. Air flow to the floor will be reduced (less fan power) and better thermal comfort will be achieved.

Rickard diffusers, by Fantech, are a provider of such motorised VAV diffusers (youtube link).

 

  • Use on floor plant (reduces fan power, responds to floor temperatures, not common or averaged temperatures)
  • Slower heat up/cool down times (so what if you’re not at exactly the right temperature for an extra half hour a day.
  • High Efficiency Chillers, pumps, fans and the like
  • Turning of your chillers at peak electrical demand and let your pipework provide free cooling (big heat sink)
  • Using tight shut off dampers on plant not in use
  • Low resistance ductwork and pipework (fan and pump power)
  • Right Sizing of plant so it runs at peak efficiency for most of a year
  • Variable speed everything
  • Simple and Robust controls with reporting. Provide an energy dashboard for all tenants to view
  • COMMISSIONING AND PROVING

Most high star rated buildings achieve their stars from the simple initiatives above. For me star ratings don’t mean much (all sorts of bizarre points available)…your aiming for low utility bills and low CO2 …..NABERS Star Rating.

Looking at it the other way…WHY don’t all commercial buildings achieve 5 stars?

  • Poor façade
  • Inefficient Lights
  • Low COP plant used including step control of compressors (now NCC requirement for plant exceeding min cooling load)
  • Poor thermal zoning of air handling plant including combining zones
  • In ability to turn down systems on reduced load
  • Poor controls and control sensors out of calibration
  • Stuck dampers allowing in too much outside air
  • High supply air temperatures used (increasing fan power)
  • Humidity control systems causing over cooling and re heating
  • No economy cycle provided (now NCC requirement for plant exceeding min cooling load)
  • Plant and systems oversizing

Author: Jorgen Knox

Last Up-dated: 4/03/2016

Contact: e: jorgenk@knoxadv.com.au, t: 02 800 33 100, w: KAE, LI