3. Systems

District Heating System

Charlestown uses its own district heating system, which sources heat in the most environmentally aware manner possible.

Electricity and heat are generated using an ENER-G 225kW Combined Heat and Power (CHP) plant, which delivers low carbon heat and electrical energy directly into the complex. During cold months when more heat is required, a 1 MW wood pellet boiler and standby 1 MW gas boilers are used to provide additional back-up.

A district heating system then delivers the generated heat and hot water to the anchor tenant, retail units and the apartment blocks.

The system delivers hot water to the 285 apartments. Hot water is pumped to the apartment cores 24/7/365 irrespective if it is required. In summer, about 50% of the thermal energy used is billed, in winter this rises to about 70%.

1. Anchor Tenant, controlled by Dunnes BMS.
2. Sub plant Room B1000
3. Sub Plant Room B2000
4. Sub Plant Room B3000
5. Sub Plant Room B4000
6. Sub Plant Room B5000
7. Retail Circuit (Air handling Units)
8. Landlord (Warm Air curtains, Air Handling Units & Hot Water)
9. Dry Air cooler (heat / cooling source for Air conditioning equipment in Retail units)

Sub Plant Rooms B1000 to B5000

A heat exchange system feeds hot water to 285 Apartments. There is a double Wilo pump controlled on a Variable Speed Drive with a 3000 litre expansion vessel to accommodate thermal expansion in the system. LPHW is delivered to each apartment which is then used to heat copper calorfiers or radiators within each apartment. Thermostats and a multichannel time-clock is used by the resident to control heat delivery into each apartment. Heat is to each apartment is metered just outside the apartment. Individual apartments do not have their own heat exchanger.

Metering

There is extensive metering in Charlestown. Residents are billed every 2 months, using a remote M- BUS meter reading and datalogging system, system reads are taken and logged on the 1st of every month.

Heat meters are installed as per the diagram above. These are read manually every month as part of plant checks. The heat meters in the sub plant rooms B1000 to B5000 are installed on the secondary and are measuring the flow and return temperatures to the apartment risers. These measurements are then used to calculate heat.

Apartment Heat Interface unit with heat meter.

Kamstrup heat meter used in Charlestown

Ultrasonic flow measurement

Valve covers added to DHS.

The awkward pipe work, which included meters, strainers, heat exchangers, control valves and flanges throughout the DHS were uninsulated.

1. Missing Valve covers (control valves, BFVs, Lever Valves) – 40
2. Heat Meters (ultrasonic) – 15
3. Strainers – 15
4. Heat Exchangers – 5
5. Flanges – 36

Within the B1000 to B5000 sub plant rooms, 23 jackets were added to the secondary (metered) side

of the heating system supplied by GEM www.insulationjackets.ie

The heat savings from the 23 jackets could be isolated from the overall savings as historical heat metering is present on the overall heat into the sub-plant room as well as the heat usage by the apartments connected to these sub-plant rooms.

Empirical guide to heat loss

Published guide tables give heat loss (w/M) for straight pipe work at the different sizes and operating temperatures (see below). These table are also utilised to calculate losses for awkward pipe work such as valves. An exposed valve is deemed to lose the equivalent amount of heat as 1 meter of straight pipework for the similar listed diameter.

In general, when empirical tables are utilised, the normal calculated pay back scenarios for insulation jacket projects deployed on 24/7/365 heating systems yield a payback of between 8 – 12 months (depending on operating temperatures and pipe-work sizes etc).

Listed below are the 23 items which were covered on the secondary heating system at Charlestown with heat loss calculations using the empirical table.

Before and After Comparisons.

Heating degree days for each given month were plotted against monthly kWh combined totals for B1000 –B5000 for the pre and post installation periods. A comparison was also made for the energy used by the apartments during the same periods to ensure that savings attributed to the jackets were not caused by a reduction in energy use by the apartments for whatever reason.

Before jackets installed. (kWh measured and added for each sub-plant room).

After jackets installed. (kWh measured and added for each sub-plant room).

Summary -4.09% Annual Saving -91,197 kWh Annual Saving

The regression equation of the line prior to the deployment of the Insulation Jackets (ECM) is used to calculate the expected consumption that would have occurred had the installation not taken place i.e. the expected kWh. The expected monthly totals were subtracted from the actual monthly totals to give the saving difference for each given month. Total savings were calculated at 91,197 kWh.

Energy metered to Apartments after Jackets Installed.

6.5% extra energy billed to (and used by) apartments after jackets installed. This is despite less energy metered to the upstream sub-plant rooms.

GEM Thermal Jacket Specification

Description: Kevlar coated stainless steel sewing thread

Temperature Resistance: The steel core can withstand prolonged temperatures of 1100°C without high strain and 600°C with mechanical strain

GEM Jacket Pull Chord:

Description: NomexTM pull chord

Detail: 8 plait braided chord from spun NomexTM yarns

Temperature Characteristics: NomexTM is an inherently flame retardant fibre that enables the product to withstand higher temperatures before degradation. Charring begins at 370°C. There is little or no melting and in the absence of a flame source, no flaming up to 500°C.

GEM Fabric Infill:

Description: Stone wool mat

Thickness: 50mm

Nominal Density: 80 kg/M3

Reaction to Fire: Reaction to Fire, Euroclass A1 EN 14303:2009 (EN 13501-1)Thermal Conductivity: At 50°C, 0.043 W/MK EN 14303:2009+A1:2013 (EN 12667)

At 100°C, 0.047 W/MK EN 14303:2009+A1:2013 (EN 12667)

At 150°C, 0.055 W/MK EN 14303:2009+A1:2013 (EN 12667)Maximum Service Temperature: 550°C

GEM Insulation Jackets Installed:

www.insulationjackets.ie

All GEM covers are bespoke. A number of measures are taken from the exposed valve to ensure a 50mm overlap to the adjacent straight insulated pipe-work or cladding.

All protrusions, pins, packing glands, screws and levers etc. are noted and recorded so as to allow for cut outs during manufacture. All jackets are made in one piece where feasible.

Larger jackets have supportive quilting pins inserted to maintain the integrity of the jacket infill. Insulating infill with more than one piece has staggered joints to prevent hot spots occurring.

GEM Jacket Benefits:

• Good mechanical wear resistance
• Resistant to most chemical attacks
• No combustible
• Easily cleaned
• Quick fitting and easy release
• Noticeable drop in operating temperature of plant room
• Increased protection from heat fatigue
• Increased safety protection from burns and protrusion hazards
• Increased temperature protection of vulnerable micro electronics

Conclusion:

Bespoke thermal insulation jackets provide a logical and simple energy conservation measure with multiple applications when applied to HVAC systems. This case study has examined the savings in a continuously operated hot water system at 65° C.

This case study would suggest that the accepted empirical guide is firmly on the conservative side of actual savings.

It would further suggest that many plant rooms with exposed valves etc. are losing far more heat that would have been expected using the commonly accepted empirical guide.

Note:

This Charlestown Energy Upgrade Project which was part of a comprehensive programme of energy upgrades and was grant aided through the SEAI EXEED programme. Excellence in Energy Efficiency Design (EXEED) enables organisations establish a systematic approach to design, construction, and commissioning processes for new investments and upgrades to existing assets. The Certified program aims to influence and deliver new best practices in energy efficient design management. EXEED designs, verifies, and manages optimum energy performance and management at the earliest stages of the lifecycle.

SEAI currently provide an EXEED grant scheme up to the value of €500,000 per year per project.https://www.seai.ie/grants/business-grants/exeed-certified-grant/ for more information.Copyright © 2018 by Distributed Energy Company Group ltd.

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