In this exercise: our design focus is to achieve a Cash-Flow-Neutral Decarb. solution for a Client to shut-down a F.F. Boiler to ZERO emissions. 

The Client’s requirement is to provide  Ren.Energy  wet central heating plus sanitary/potable HW, to a Historic building thro. a sub-zero winter location…asking an especially beneficial HIGH Seasonal C.O.P. (SCOP p.a.) I.R.R. to attract additional future stakeholder’s investment into the Property.

Our Client has instructed their preference for a “minimum-disturbance”  installation of an ASHP holistic System to be considered, whereby we must first develop a proven LCC Analysis & Concept Design for examination by the current  Property Directors before any further decision can occur.

For such an Analysis we begin with Baseline Data. We must develop accurate input load calculations for audited Zones of the Property, (per ASHRAE Stds.) for all key metrics. Separate to possible sub-zone metering evidence, our Analysis shall require 2-3 years utility bills of energy input & consumption at concurrent occupation & confirmation of same future functional operations (or with suggested variance).

Our Concept proposal requires a design that Adds-Value by using full benefit from BOTH sides of an ASHP exchange (i.e. both Water heating & Air Cooling IAQ/IEQ). As before & as always, our design imperative is to incentivise private investment capital into the project…by validated accuracy of our new Design’s reduction in operating cost metrics.

Design Decision (1): Macro-Strategy for FASTER Investment Return:

D1.1) DECOUPLE the central heating circuit’s secondary closed loops from the sanitary/potable HW open supply loops ( by separate Tech. Thoughts we instruct correct additional methodology for heating this Sanitary HW.);

D1.2) REDUCE TEMP. of central heating secondary circulating closed HW loops from Boiler Flow @65-75C down to H.P. Flow @35-45C primary loop circulation (operate the ASHP at lower Delta T.);

D1.3) SIZE & POSITION multiple linked vertical tanks as hydraulic-break for an oversized buffer storage between primary & secondary loops;

D1.4) REDUCE FLOW RATE on ALL Flow/Return recirculation loops for Buffer HW storage;

D1.5) MANIFOLD control of Space Heating HW downstream recirc. loops through balanced L.T. Emitters/UFH.

D1.5) UPCYCLE & DND all ancillary passive fittings & ancillary equipment, that is in appropriate condition for long-term operation;

D1.6) CREATE INNOVATIVE FUTURE-PROOF new piping & ducting routes with a design that keeps an officially proven safe distance from any  structural heritage features (or ancient sacred relic) to thereby safe-guard such areas as future-proof for restoration;

D1.7) INTEGRATE PROVEN TECHNOLOGIES for final delivery of appropriate radiant heat + IAQ/IEQ & surplus moisture removal to all setpoints & building locations of Design; e.g. UFH cannot be prescribed for ancient Roman mosaic flooring.

FORENSIC ANALYSIS (1): Diagnose Load Demand Audit to calculate a design compliant, functional HW Storage Capacity & Buffer Tanks optimum location:

A1.1) Daily Space Heating Load Demand: to be calculated as total aggregate kWh metric of wet central heating emission required (@ worst winter temperature) to sustain property interior @ 21-23C 24/7 for all space heating rooms/zones interconnected for downstream of the HW Buffer Storage ……. (verified by Analysis of previous years’ F.F. utility records for central heating consumption & adjusted for new L.T. Emissions from previous boiler higher heat distribution (@65-75C Flow) including previous consumption (Total Litres/Day) of sanitary HW consumption Load; (we shall explain exact overall calculation & logic in a future Tech.T. exercise);

  A1.2) Load Shift Capacity: calculated as EXTRA stored HW capacity to sustain daily 24/7 central heating during timed-out H.P. run-time to avoid “peak-tariff” costs;

 A1.3)   Resilience Capacity: calculated as EXTRA stored HW capacity to  sustain 1-2days of central heating “run-time” across future outage & delayed resumption of Service (for remote location);

FORENSIC ANALYSIS (2) : Survey Audit of “thermal chokepoints” by micro-analysis of all existing downstream HW loop(s):  

N.B. The above Forensic Analysis is to re-calculate the BUFFER TANK(S) volumetric sizing, plus the Tank(s) location & piping redesign. Buffer storage is the most critical factor to impact the efficiency of the Holistic System.

 A2.1) Existing Calorifier/Boiler Buffer: check maintenance records & inspect to confirm any existing storage has a future long-term, trouble-free durability to integrate within new upgraded HW storage capacity;

A2.2) Aggregate Volumetric Buffer Capacity: after combining total volumes & weight of A1.1-A1.3check for static structural (stress) analysis for the proposed Buffer Tank(s) mounting area to verify safety margins;

 A2.3) Tank Sizing by Building Access: select individual tank sizing to fit elevators & doorways etc. for minimum cost (2 men & trolley can usually access through standard size doors in/out multiple 500L empty Tanks into exact final line-up location as per photo #2 V-E Menu Tab) with allowance for a minimum installed 750mm headroom above each tank for vertical HW piping & valve fittings;

 A2.4) Tank Location & Spacing: for easiest plumbing, the optimum location is closest proximity to the pipework & F.F. boiler under shutdown, with adequate all round spacing for tank servicing & future-proofing for easy replacement. Alternate, locations are wherever shortest pipelines are possible to lower the cost of pumping power, including basements, outbuildings or even submerged below ground always to include at least 4+ individual Tanks and the extra Tank(s) for sanitary HW;

Design Decision (2) Operate H.P. only on “OFF-PEAK” Tariff:

D2.1) maximise “EFFECTIVE” stored volume by a re-designed interconnection of buffer tank piping. Connect as In-Series/In-Parallel multi-tanks (Fig.1 below & Photo #2: Value Engineering) to link together (tallest possible, same size, Vertical Tanks) multiple (4+) Tanks in an N+1 array of 500L; or 5,000L; or 10,000L Tanks.

N.B. the “EFFECTIVE” NET HW stored volume (@set-point) must EXCEED TOTAL daytime (peak tariff) circulated heating demand, so that H.P. is ONLY operating during off-peak hours.

 

D2.2)  oversize buffer tanks storage effective volume versus H.P. output volume during scheduled off-peak run-time, to eliminate risk of  H.P. shortcycling with the buffer tank. This also allows flexible optimising of each central heating loop to operate 24/7 at independent Flow-rate & DeltaT. in a sustainable, steady-state durability for a higher System C.O.P.;

D2.3) install baffle diffusers within the inlet/outlet of each tank to eliminate turbulence & thermocline disturbance to prevent stored HW temperature dilution within tank interior;

D2.4) dial down BOTH (Primary & Secondary) circ. pump’s Flow-Rate to minimal optimized rate (L/s) also by manifold control, for each loop around each “balanced” emitter for highest System C.O.P.;  

For the next and subsequent Tech. Thoughts, we shall progress our comments for the complete LCC Analysis & Concept Design to advise on the actual Heat Pump’s Primary Loop to sustain all Buffer Tank(s) @ H.P. Flow @35-45C set-point 24/7 (although only on “OFF-PEAK” run-time for 5-6 hours/day);  followed by our techniques for a sanitary HW independent Tertiary Loop sustained @58-60Celcius (Legionella proof). Then we continue to explain the necessary expertise to integrate a higher performance Solar energy contribution to further the Cash-Flow-Neutral decarbonization solution at the highest possible SCOP for a BESPOKE retrofit to this Building at this Site.

CAUTION:

Most well-designed H.P. models, with carefully selected specifications, deliver exceptionally robust & durable long-term performance when installed diligently. However, they are M.& E. devices that require the manufacturer’s recommended regular maintenance; BUT Even more frequent servicing is needed for Filters, in-line Strainers, Valves, Fans, & Pumps etc. when installed under harsh environmental conditions.

For smooth future-proofing advanced Tech. upgrades, the overall System Design must allow for sufficient maintenance access on all sides of the equipment. In difficult locations of maritime humid salty air, or industrial-zone air pollution contaminants, or desert-haze conditions or high TDS water content, extra care is needed by an annual pre-emptive, comprehensive maintenance protocol. (to be advised)

Our decades of experience & almost 4,800 installations in varied System Application Designs (bespoke for site-conditions) across USA, UK, Korea, Australia, Mid-East & Mediterranean elite & historic properties have proven that a Commercial H.P. installation, (with an appropriate schedule of maintenance for the site conditions), can have a longevity beyond 25years (with only normal “wear & tear” parts replacement). By this experience, an Owner/Operator can expect a high performance I.R.R. or R.O.I. on the first cost CAPEX, multiplied many times across the durability (L.C.C.) of the Heat Pump.

N.B.  Engineered Designs are in compliance to ASHRAE/CIBSE Standards & Local Building Regulations & Codes.

[Tech. Thoughts was transcribed by Team Leader David Wilton. The content is protected by Copyright and is not legal to be reused. If you wish to co-operate with our Heat Pump Academy and would like to copy and reuse some parts of our content please use our contact form to make a request.]