Transcript Strategic Design of Environmental Systems

Designing for HVAC and Renewables
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 ….
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
Building Systems
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.
Basic Objectives
• provide adequate ventilation for health and comfort (indoor air
quality)
•
fresh air supply (8l/sec.person)
•
temperature control (Tres  17-22°C)
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)
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)
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
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
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
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 ….
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
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 ...
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)
Owner’s Requirements
• Owners, developer’s 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/environmental impact is often low
down on the list of priorities
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
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)
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.
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)
Building Regulations
• UK building regulations:
• insulation requirements (Building Reg’s / SAP)
• ventilation levels
• systems, etc.
• National and Local Planning
• Building designation (retrofit)
• Special Location
• Local regulations (London Energy Strategy)
• European Regulations (Buildings Performance Directive)
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 ….
Selecting/designing a system
selection
design team
design process
support
environment
implications
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
Technical Assessment
• simulation enables a design team to make informed choices on a likely
system’s performance accounting for the complex interactions between the
fabric-occupants and systems
Technical Assessment
Mathematical model
Performance assessment
Technical Assessment
•Key outputs from a simulation
•temperatures
•heat fluxes
•air movement
•humidity
•power flows
•Comfort
•Energy consumption
•Health and Safety, etc, etc.
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.
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
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
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
Example CHP System
Design choice: CHP
system
Modelling and
simulation
Assessment: technical
feasibility, cost, fuel
and CO2 savings
Yes/no
Case Study: Lighthouse Building, Glasgow
policies being enacted to foster
Lighthouse Building
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.
Base Case Design
• Diagram or schematic, if
appropriate
Appraisal of Options

Base Case
W/m2
Energy Demand per Unit Time
Annual Energy Performance
200
180
160
140
120
100
80
60
40
20
0
He ating
T ransition
Winter
1
3
5
7
Lighting
9 11 13 15 17 19 21 23
2
4
6
Summer
8 10 12 14 16 18 20 22 24 1
3
5
7
9 11 13 15 17 19 21 23
Time (h)
2
Heating:
118.29 kWh/m .a
Cooling:
0.00 kWh/m .a
Lighting:
100.10 kWh/m .a
2
2
2
Fans:
0.00 kWh/m .a
Small PL:
0.00 kWh/m .a
DHW:
0.00 kWh/m .a
Total:
218.39 kWh/m .a
2
2
2
 As

above +
advanced glazing
W/m2
Energy Demand per Unit Time
200
180
160
140
120
100
80
60
40
20
0
Annual Energy Performance
He ating
Winter
1
3
5
7
9 11 13 15 17 19 21 23
Lighting
T ransition
2
4
6
8 10 12 14 16 18 20 22 24 1
Time (h)
Summer
3
5
7
9 11 13 15 17 19 21 23
2
Heating:
49.07 kWh/m .a
Cooling:
0.00 kWh/m .a
Lighting:
100.10 kWh/m .a
2
2
2
Fans:
0.00 kWh/m .a
Small PL:
0.00 kWh/m .a
DHW:
0.00 kWh/m .a
Total:
149.17 kWh/m .a
2
2
2
Energy Demand per Unit Time


above +
Solar wall +
W/m2
 As
lighting control
200
180
160
140
120
100
80
60
40
20
0
Annual Energy Performance
He ating
Winter
1


efficient lighting +
responsive heating
5
7
9 11 13 15 17 19 21 23
T ransition
2
4
6
8 10 12 14 16 18 20 22 24 1
Time (h)
Summer
3
5
7
9 11 13 15 17 19 21 23
2
Heating:
64.52 kWh/m .a
Cooling:
0.00 kWh/m .a
Lighting:
41.59 kWh/m .a
2
2
2
Fans:
0.00 kWh/m .a
Small PL:
0.00 kWh/m .a
DHW:
0.00 kWh/m .a
Total:
106.12 kWh/m .a
2
2
2
Energy Demand per Unit Time
above +
W/m2
 As
3
Lighting
200
180
160
140
120
100
80
60
40
20
0
Annual Energy Performance
Heating
Winter
1
3
5
7
9 11 13 15 17 19 21 23
Lighting
T ransition
2
4
6
8 10 12 14 16 18 20 22 24 1
Time (h)
Summer
3
5
7
9 11 13 15 17 19 21 23
2
Heating:
48.99 kWh/m .a
Cooling:
0.00 kWh/m .a
Lighting:
19.96 kWh/m .a
2
2
2
Fans:
0.00 kWh/m .a
Small PL:
0.00 kWh/m .a
DHW:
0.00 kWh/m .a
Total:
68.96 kWh/m .a
2
2
2
Final Outcome
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) e-mail report to [email protected]