Designing for HVAC and Renewables

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Designing for HVAC and Renewables
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Strategic Design of Building Systems

• This lecture looks at the design and assessment
  of building environmental systems (HVAC).
• Also look at some of the new concepts emerging in
  the built environment
• distributed generation/renewables integration
• demand management for better demand-supply
  matching.
• Firstly what are building environmental systems
  .

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sources boilers, chillers, electricity supply
distribution cables, ducts, fans, pumps, piping,
etc.
delivery radiators, underfloor heating, lights,
diffusers, etc.
control thermostats, dampers, valves, timers,
PID controllers, etc.
environmental system
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Building Systems
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HVAC System Requirements

• What are the design requirements for a building
  and its environmental systems
• to provide healthy, comfortable environment for
  the occupants
• The operation of the environmental system can be
  subject to constraints (this will affect the
  design)
• e.g. at a minimum running cost
• with minimum environmental impact (EBD)
• no constraints
• this used to be the case and leads to high
  energy consumption and high costs - the
  environmental system rectifies problems inherent
  in a building design - poor fabric, overcrowding,
  etc.

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Basic Objectives

• provide adequate ventilation for health and
  comfort (indoor air quality)
• fresh air supply (8l/sec.person)
• temperature control (Tres ? 17-22C)
• contaminant dispersal (safe levels)
• provide adequate acoustic environment (usually
  related to the operation of ventilation systems)
• provide adequate lighting levels for safety and
  performance of tasks (150-600lux)

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Buildings and Environment

• There is increasing concern over the
  environmental impact of buildings (macro and
  micro).
• The built environment accounts for over 50 of
  delivered energy (mainly space heat, electricity)
• Energy consumption has consequences NOx, SOx,
  CO2 emissions, poor air quality (impact of fossil
  based CHP?)
• It is the systems in the building which account
  for the bulk of the energy consumption
• Previously viewed purely only as a consumer of
  energy this is changing ...(future electrical
  networks with embedded generation)

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Buildings and Environment

• Now possible to produce much of its own heat and
  power from energy efficient or clean
  technologies
• CHP
• Photovoltaics PV
• Micro turbines
• Ducted Wind Turbines
• Fuel Cells
• Heat Pumps - air source and ground source
• Solar thermal/passive solar

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sources boilers, chillers, electricity supply
distribution cables, ducts, fans, pumps, piping,
etc.
delivery radiators, underfloor heating, lights,
diffusers, etc.
control thermostats, dampers, valves, timers,
PID controllers, etc.
Localised generation of heat and power
distributed/ embedded generation
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Buildings and Environment

• It is equally important that the overall demand
  (energy intensity of buildings is minimised)
• passive solar technology
• well insulated, well maintained fabric
• day lighting, efficient lighting
• well maintained, efficient distribution systems
• natural ventilation
• mechanical ventilation/heat recovery
• energy saving controls
• high efficiency heating and cooling devices

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Building Systems Design

• The need to satisfy human comfort while consider
  environmental impact and meet a host of other
  criteria means that building design is a complex
  process
• Fundamentally a building is complex, integrated
  energy system (the possibility of distributed
  generation and need for reducing demand only
  makes it more so)
• It will not work unless properly designed and
  analysed
• The majority of buildings in the UK are poorly
  designed over specified HVAC plant, poor
  occupant comfort, high energy consumption,
  reliant on tight control and system over capacity
  to accommodate basic design faults
• requires an integrated, team based design
  process .

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Strategic Design of Environmental Systems
The OLD school
The NEW approach
architect designs building
design team
engineers design services
fabric and systems design evolves together
poorly performing buildings and systems!
better performing systems, less energy used,
smaller environmental impact
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Strategic Design

• The design of a building takes the following into
  account
• site and location (renewables integration)
• energy and other utility supplies (dictated by
  plant type)
• owner requirements (function, cost)
• occupant characteristics and requirements
  (comfort, health and plant capacity)
• building regulations (minimum requirements)
• environmental impact and regulations (EC EPD)
• ALL of these factors will affect the design and
  performance ...

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Building Site and Form
Building location warm/cool climate urban/rural
site available energy resources and
services Building form building
orientation building form (shallow plan/deep
plan) glazing areas/shading structure
(heavyweight, lightweight) infiltration (surface
area/volume)
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Owners Requirements

• Owners, developers requirements
• building function
• cost limits
• environmental strategy
• NB distributed generation, renewables integration
  and energy efficiency, all increase the capital
  cost of a building
• Very often energy costs are much less than other
  costs e.g. wages and so energy consumption/environ
  mental impact is often low down on the list of
  priorities

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Building Fabric

• Building category and use
• domestic (cost/ profit margins)
• Commercial/ industrial (speculative/custom built,
  etc.)
• Space usage (kitchen, office, toilet, etc)
• Layout
• Flexibility of use (changes of use in building
  lifetime)
• Special features
• atria
• solar chimneys
• sun spaces

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Occupants

• occupant density (ventilation requirements,
  cooling/heating requirements)
• occupant activity (design temperatures,
  ventilation, cooling/heating levels)
• occupant type (children, adults, old/sick)
• occupation of the building (intermittent, 24
  hour)

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Energy Supplies

• Grid availability, grid connected
• Gas availability (network connection not always
  available)
• Solid fuel availability
• Other local resource, e.g. district heating, CHP
• Solar resource (geography, climate, site)
• Other resources - wind, biomass, etc.

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System Requirements

• heating and/or cooling
• quick response (dynamics - building fabric)
• delivery mechanism (convective/radiant/mixed)
• ventilation (mechanical, natural, contaminants)
• humidification/dehumidification and air
  conditioning
• Lighting (daylighting, task lighting)
• special processes (industrial, commercial)

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Building Regulations

• UK building regulations
• insulation requirements (Building Regs / SAP)
• ventilation levels
• systems, etc.
• National and Local Planning
• Building designation (retrofit)
• Special Location
• Local regulations (London Energy Strategy)
• European Regulations (Buildings Performance
  Directive)

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Evaluating a design...

• the design of for a building and selection of
  systems and components is an iterative process
• probably the most important evaluation is the
  performance evaluation
• this is best done looking at all the elements of
  the building design as they evolve together
• this type of design model requires feedback on
  the likely performance of a system .

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Selecting/designing a system
selection
support environment
design process
design team
implications
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Performance Evaluation

• an appropriate support environment for the
  building design process is building environmental
  simulation
• simulation is the mathematical modelling of a
  building operating in realistic dynamic
  conditions
• allows the design team to assess environmental
  performance (human comfort, energy consumption,
  emissions, etc.)
• building form and fabric
• orientation and site
• occupancy
• systems (HVAC RE)
• controls action

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Technical Assessment

• simulation enables a design team to make
  informed choices on a likely systems performance
  accounting for the complex interactions between
  the fabric-occupants and systems

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Technical Assessment
Mathematical model
Performance assessment
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Technical Assessment

• Key outputs from a simulation
• temperatures
• heat fluxes
• air movement
• humidity
• power flows
• Comfort
• Energy consumption
• Health and Safety, etc, etc.

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Environmental Impact

• Environmental Impact
• the quantity of resources used in the
  construction and running of a system (fossil
  fuels, metals, plastics)
• the emissions from the system which are harmful
  to people and the environment
• the ease of disposal and ability to recycle
  elements of the system
• The selection of the environmental systems will
  have a significant affect on the environmental
  impact of the building.

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Environmental Impact

• High Impact
• full air conditioning (heating/cooling
  humidification, etc)
• electric heating (from non-renewable sources)
• incandescent feature lighting
• Medium Impact
• mechanical ventilation
• heating using fossil fuels
• fluorescent lighting

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Environmental Impact

• Low impact
• solar water heating
• natural ventilation
• daylighting
• use of thermal mass/ thermal insulation
• photovoltaic power production
• combined heat and power
• daylight-linked controls
• occupancy sensors
• energy management systems
• strongly linked to the orientation and design
  of the building fabric

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Costs

• Capital cost
• system and installation costs
• Running costs (Whole life costs)
• fuel costs electricity, gas
• maintenance costs
• High environmental impact systems tend to be
  high cost systems, e.g. air conditioning has high
  capital and running costs
• Some Low environmental impact systems have high
  capital costs e.g. CHP, energy management systems
  building integrated wind turbines and
  photovoltaics

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Example CHP System
Design choice CHP system
Modelling and simulation
Assessment technical feasibility, cost, fuel and
CO2 savings
Yes/no
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Case Study Lighthouse Building, Glasgow

• policies being enacted to foster energy
  efficiency and clean technologies for
  environmental impact mitigation
• implementation at the local level is problematic
• cities can best respond by
• - using simulation to appraise
• options
• - and establishing databases to
• appraise replication
• aim is to help planners and designers to match
  renewable energy resources to reduced demand.

Lighthouse Building
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Base Case Design

• Diagram or schematic, if appropriate

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Appraisal of Options

• Base Case

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Final Outcome
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Assignment
Using the internet and other resources find a
case study of a low energy building and write a
short report on about the systems associated with
it. Include the following in the report.
Describe the main energy consuming HVAC systems
in the building, their function and the types of
energy which they use. Mention if renewable
or distributed generation systems have been used
and describe them. Describe what techniques
have been used to minimise energy consumption and
try to explain how they work. (500 words max)
upload report to http//iqsoft.co.in/students/assi
gnment.php