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MtCO 2e /yr in comparison to supplying the energy outputs in a con- ventional manner [6]. A network and market for trading in heat, along with the wider use of district heating systems, could also open sig- ni fi cant potential for exporting heat from industrial sites to other users. A range of Best Practice Technologies (BPTs) – those that represent the ‘ best ’ technologies, which are currently in use and therefore econom- ically viable – for both energy e ffi ciency improvements and heat re- covery has been advocated for introduction into the pulp and paper sector in future [21,26,30 – 32]. 3.3.4. Demand-side fl exibility Demand-side fl exibility (DSF) is the ability to change electricity de- mand from an industrial plant or other user in response to an external signal from a power supplier [46,47]. The use of tools such as Demand Side Response (DSR) – where levels of electricity demand are increased, reduced or shifted - and on-site energy storage enable the optimisation of electricity usage and has major advantages in the context of an en- ergy infrastructure designed to meet occasional peak demands. This will be particularly important in the transition towards a low-carbon future. Demand Side Participation (DSP) concepts are mainly short-term (minutes to hours) [48], whereas fl exibility is needed over several days or more. The rigid patterns of power supply based on life-long experi- ence of fossil-fuelled supplies make such fl exibility challenging, but are important to explore. Fully automated DSR concepts, such as ‘ smart ’ controllers for EV charging and heat-pumps, have been studied in some detail. Industrial and commercial (I&C) customers can bene fi t fi nancially byo ff ering DSF services to market actors (e.g., the various ‘ aggregators ’ - companies who aggregate small loads and then participate in demand- side markets on behalf of customers - or the National Grid , the ‘ System Operator ’ for the Great Britain (GB)). Distribution Network Operators (DNOs), who run and maintain regional distribution systems, can em- ploy DSF to manage local network restrictions. This can reduce stress at peak times, support planned or unplanned network outages, and defer or avoid the need for network reinforcement [46]. In both cases, the operators are motivated by the growing share of so-called ‘ non-pro- grammable ’ renewable energy sources (NP RES) on the network [49]. The contribution of DSF in GB electricity markets is currently small and mainly for grid balancing on a second-by-second basis. It is therefore a largely ‘ untapped ’ resource. DSF will inevitably be required in future in order to manage the system and market risks [38]. Smart power in- novations - a combination of interconnectors, storage and demand fl exibility (or DSR) - could generate £8 bn per year of savings; according to a report for the recently-established UK National Infrastructure Com- mission [50]. The National Grid (NG) in GB aims to address various barriers to customer participation, and is initially focusing on interacting with I&C customers [46]. Those customers who o ff er demand-side fl exibility gen- erally do so to reduce their electricity costs and generate new revenue streams, enabled by new ICT (e.g., metering and automation). But pilot demonstrations will be necessary in order to overcome the fears of some I&C customers that disturbances to their production processes might lead to reduced outputs or quality. Many such customers work with ‘ aggregators ’ , because current DSR markets in the UK are seen as complex, or their volumes are too small to access DSF tools directly [46]. On-site or ‘ back-up ’ generation provides much of the DSF today [46]. Nevertheless, leveraging further on-site CHP or co-generation plants from the paper industry will enable the sector to interact more easily with the energy market [49]. The Confederation of European Paper Industries (CEPI) has suggested that mechanical pulping, an electro-in- tensive process, can be used for ‘ peak shaving ’ programmes [33]. It can react at reasonably short notice, ranging from as short as 15 min up to one hour, depending on the frequency and schedule of interruptions. In some European countries (e.g., Austria, Belgium and Norway), the paper industry is also involved in ‘ valley fi lling ’ programmes, whereby the whole production process is shifted to the night or to the weekends so as to optimise baseload electricity generation [49]. But, in the paper-
noted that the costs of such gasi fi cation are high and rather unreliable. Presently all direct heat, around 13.5% of that is generated in the UK paper industry, is produced from the burning of NG. Some 2.2 TWh is produced from biofuels - constituting 23% of all fuels utilised in the sector. Indeed, the CPI have suggested to the UK Government that it could be a promising candidate for an above average share of biomass for electricity and heat (> 7% by 2030). That would be equivalent to a growth of biomass use of around 4% per annum, or some 22,000 tonnes of additional resource. According to the CPI, the main technological opportunities going forward are likely to be in the areas of CHP and, in the longer term, CCS. Residuals from paper-making can be employed as a new feedstock for low-quality paper, as a source of minerals, or else applied in the construction sector. A downside of paper waste utilisa- tion is the production of ash from its incineration, which is con- taminated with heavy metals from dyes, inks and surface treatments. 3.3.3. Energy e ffi ciency and heat recovery In meeting the twin challenges of climate change mitigation and energy security, the UK Government ’ s Carbon Plan [38] set out a number of guiding principles. The fi rst among them was to use less energy in the most cost-e ff ective manner in industry as elsewhere. This central role for energy e ffi ciency improvements were echoed at an in- ternational level by the International Energy Agency (IEA) [39], by the EU [40], and countries like Germany [41] and Sweden [42,43]. The IEA have attempted to capture the highest potential reduction in global emissions from e ffi ciency measures in their clean energy pathways or roadmaps out to 2050 [39]. They argue that the cost savings accrued from reducing energy demand could outweigh additional costs by 2.5:1 and, after discounting future savings to present money with a 10% discount rate, save several trillion US dollars. The IEA suggest that the implementation of Best Available Technologies (BATs) - those that are proven technologies, but which may not yet be economically viable - could reduce energy consumption by 20% from current levels [39]. They argue that the BATs o ff er some of the most promising least-cost options for reducing energy consumption and GHG emissions in in- dustry. But action is needed to invest in new facilities and to retro fi t equipment that reach BAT levels, otherwise this capacity will be sub- optimal and very costly to upgrade. Energy e ffi ciency measures have therefore been widely re- commended for the pulp and paper sector and other industries [38 – 43]. Likewise heat recovery opportunities are seen as having a signi fi cant improvement potential [21,26,30 – 32]. In the UK, Hammond and Norman [6] employed a database of the heat demand, heat recovery potential and location of industrial sites involved in the EU-ETS to es- timate the potential application of di ff erent heat recovery technologies. The options considered for recovering the heat were recovery for use on-site (using heat exchangers); upgrading the heat to a higher tem- perature (via heat pumps); conversion of the heat energy to ful fi ll a cooling demand (employing absorption chillers); conversion of heat to electricity (adopting organic Rankine cycle (ORC) devices; see also Chen et al. [44]); and transport of the heat to ful fi ll an o ff -site heat demand. Similarly, the Energy research Centre of the Netherlands (ECN) have ex- amined the potential of modern industrial heat pumps that could gen- erate steam up to 200 °C utilising waste heat [45], including a test cell programme related to the particular needs of the paper industry. The UK analysis by Hammond and Norman [6] provided an indicative assess- ment of the overall potential for the various technologies. The greatest potential for reusing surplus heat was found to be recovery at low temperatures (via heat exchangers), and in its conversion to electrical power (mostly utilising ORC technology [44]). Both these technologies exist in commercial applications, but are not well established. Support for their further development and installation could therefore increase their take-up. A broad analysis of this type, which investigates a large number of sites, cannot accurately identify all site-level opportunities. Nonetheless, the overall heat recoverable in the UK using a combination of these technologies was estimated at 52 PJ/yr, saving over 2.0
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